00 Prologue

My faithful student,

I am writing to inform you that I may be out of communication for a short time. I have been spending what little free time I have over the last few decades on a project that I believe has the potential to revolutionize Equestria, and it's reached a delicate stage that requires my direct attention. Any letters to me will be forwarded to Princess Luna for the duration; she will be taking care of the day-to-day running of the country while I am occupied.

Do not neglect your studies. I look forward to hearing your reports on the magic of friendship, and sharing with you what I have been working on, when I return.

Princess Celestia

• • •

Twilight sighed as she placed the letter back in its file. Ten years, she thought. Ten years since she'd received the letter, ten years since she'd heard anything from her missing mentor. Ten years since Princess Luna had summoned her, frantic in the cool, restrained way of royalty with an image to maintain.

• • •

"She told me she would be working in her subbasement office that night, and that she didn't wish to be disturbed." The younger princess led them through the lower levels of Canterlot Castle. The air grew decidedly musty and damp; it was clear to Twilight that ponies rarely came here.

The pair came to a heavy oaken door, and Luna's horn glowed and the door slowly creaked open. "After a day, I began to worry. She hadn't shown for any meals, though I could still sense her presence within the castle. I came down to check on her, and there was no response when I called. When I entered the room, I found it as you see it now... empty."

Hesitant, Twilight entered her mentor's private study and looked around, not sure what she would find. There was a desk with some neatly-stacked scrolls and parchment, a cushion before it, and a bookcase along the wall filled with well-worn tomes. The walls were bare, rough-hewn stone, and Twilight realized they must be at the very foundation of the castle.

"When I've attempted to perform a locator spell on her, I am drawn here, but there are obviously no signs of her. The results of the spell are unusual, as well – rather than specific location, I get a generalized sense of her presence, but no direction to guide me to her."

Twilight moved to the desk, Luna watching from the door, and inspected the papers. They were riddled with bizarre language, words and acronyms she didn't recognize, and complicated diagrams filled with unfamiliar symbols, but she thought she could make out the basic idea. "It looks like she was trying to construct some sort of... calculation machine?"

"That is the best I have been able to determine," Luna said, hints of sorrow and confusion tracing through her voice. "My sister had not involved me in this work. I do know she had started it long ago, while I was still imprisoned. I personally lack the relevant knowledge or know-how to be able to understand her notes, and I have been reluctant to share them with anypony. My sister clearly wanted this kept secret and for all I know it could be dangerous to the wrong pony.

"I believe you may be the right pony."

Twilight turned. "Princess?"

"Celestia spoke of you often. I know how impressed she was with your abilities and accomplishments, how proud she was of your progress. She trusted you implicitly and therefore I do too." Luna bowed her head for a moment, then looked at the young mare before her with a steady gaze and a lone tear dripping down her muzzle. "I brought you here to ask if you would take Celestia's notes, her research, and attempt to follow in her hoofsteps, as it were. I am a thousand years out of date. It would take me decades or centuries to catch up to the point where I could hope to understand enough. You are knowledgeable, bright, and more familiar with my sister than any other pony. It's my hope you may be able to shed some light on where she has gone, or what has happened to her."

It was Twilight's turn to bow her head, appearing lost in thought. When she looked back up, her eyes were shiny with tears, her brow furrowed with determination. "Of course I will, Princess Luna." She hesitated before admitting, "I don't know what I'd do without her."

Luna smiled a small, sad smile. "Nor do I, Twilight Sparkle. See if you can find her."

• • •

Ten years. Twilight knew she was being needlessly maudlin and found it hard to care. She shook her head, dropped the file back in its cabinet, and stood for the first time in hours. What time was it? In the basement of the Ponyville library, she had no way of knowing how long it had been. She idly flexed each leg, working out the kinks in her joints, before moving away from her workspace's pool of light, towards the base of the stairs in the darkness.

• • •

For a time, Luna had maintained the pretense that Celestia was away on an extended diplomatic tour of major allies around the world, but she could only maintain the fiction for so long. Twilight and the other Elements of Harmony had stood with her when she announced that Celestia was, in fact, missing, and the Regent of the Moon would be assuming responsibility for Equestria. Many of her subjects reacted with heartbroken dismay at the news their beloved ruler was never returning, though Twilight took it as a challenge, a reason to redouble her efforts.

Celestia's notes were intricate, impressive, and incomplete. Some intellectual leaps were required as Twilight worked through her research, and she worried that she may have missed things the ancient alicorn had taken for granted. Partly, her worries were fueled by the nagging suspicion that it was too easy; even with the gaps in the source material, everything had been laid out before her – she simply followed the trail. It probably helped that she'd always had a mild interest in more advanced technology, and she'd adapted her basement lab, unused since she had attempted to determine the roots of Pinkie's unusual precognitive abilities, to her new line of work.

• • •

At the top of the stairs leading from the basement to the library proper, Twilight turned and paused, looking out over her lab. The machinery all hummed warmly, and the large screen she had erected against one wall depicted an overhead view of Ponyville, updated by magic sixty times per second to create the illusion of real-time movement. It wasn't actually Ponyville, of course; she wouldn't need a roomful of arcane equipment to power a simple scrying spell. She had used Celestia's techniques to create a simulation of the small town and its inhabitants and left it running constantly. She justified it as a long-term experiment to see how accurate the simulation could be, but were she completely honest with herself, she'd have to admit she had no idea what else to do. She had reached the end of Celestia's notes and been left with no obvious next step nor any useful clues as to the alicorn's fate.

Tiny pony-shaped figures moved about their business, unaware they existed only in the heart of a machine – unaware of anything at all, in fact, as they were by no means sentient, just programs following their set directives.

Sometimes it made Twilight uneasy, seeing her friends and neighbors move about on the screen, acting much as they would in the real world. None of their real-world counterparts had any idea this existed, of course: Twilight had taken the princesses' wishes to heart and not revealed the nature of her work to anyone, even her friends. They all knew that she was doing some kind of research for Princess Luna, and that it had to do with Princess Celestia's disappearance, but she had explained that for everyone's safety, she had to keep it to herself. They had all understood and agreed to stay out of the basement, some more reluctantly than others.

Rainbow Dash in particular hated the idea of being left out of something so potentially awesome, though as time had passed and she'd seen it appeared to amount to nothing more than extra studying, she'd cooled down on the idea of helping out. What had she been expecting, some grand adventure to hunt down the Princess? Inspecting the overview of her simulated Ponyville, Twilight found Rainbow's simulated double lazing on a simulated cloud puff and shook her head, grinning. It's a fairly accurate simulation, all right.

She turned back to the door and went into the main room of the library, her hooves clopping softly on the hardwood floor. It was clearly late; the room would be pitch-black if Spike hadn't left a few candles flickering, cutting into the dimness. She moved to a window and nosed the curtain aside, looking out into the night. Clear and crisp, with few clouds in the starry sky. Luna's moon shone brilliantly over Ponyville and Twilight gazed up at it, musing on how much had changed since the first time she'd stared sleeplessly up into the sky here.

Sighing again, Twilight headed for bed, passing Spike. He'd grown quite a bit since Celestia's disappearance and now slept in a full-size bed next to hers. She tried to move as quietly as possible, not wanting to disturb him. She had no idea when he'd gone to bed, as the prohibition against entering the basement applied to even him. About to climb into her own bed, she froze, silent, as the bed behind her creaked.

"Twilight?" Spike's voice sounded bleary with sleep.

"Hey, Spike," Twilight murmured softly. "I'm sorry I woke you, go back to sleep."

"Okay, Twi..." He yawned and rolled over, swaddling himself in his blanket. "Sweet dreams..."

"You too, Spike." She yawned as well and pulled herself into bed, settling beneath the covers. Letting her eyes drift shut, she calmed her mind, allowing her thoughts to quiet in preparation for sleep.

A sudden low rumbling snapped her eyes open and she pushed herself up, startled. Across the room, Spike turned over in his sleep and let out a tremendous fiery belch. Even in her half-asleep state, Twilight reflexively ignited her horn and grabbed the note that formed out of ashes in midair, bringing it over for her to read in bed. Spike slumbered on, oblivious.

Seconds later, Spike sat up in bed abruptly, startled awake himself by a loud banging noise. He looked around wildly, saw Twilight's bed was empty, the covers thrown back; saw the front door of the library had been blasted off its hinges; saw a singed roll of parchment laying on the floor between the two beds. He jumped out of bed and picked it up, unfurling it to read, and his eyes went wide.

"No way."

• • •

My faithful student,

I need your help. Please come to my study.

Princess Celestia

01 Startup

Rainbow Dash surged forward, glaring at Applejack's tail bobbing just in front of her. "Come on, Rainbow... show 'em a little Dash!" she muttered to herself as she put on an extra burst of speed, pulling abreast of her challenger. Red, orange, and yellow leaves rained down around them as they pounded down the dirt path that snaked through Whitetail Wood. As Rainbow came up alongside Applejack, she glanced over and their eyes met for an instant – hard determination gleamed in each – and suddenly Dash was in the air, catapulting forward, watching the ground spin beneath her as she tumbled, a confused AJ looking on, landing flat on her back, wings spread, looking back the way she'd come at a gnarled tree root that had broken through the surface of the dirt.

"Aw, ponyfeathers."

With a start, Dash tumbled out of bed, landing flat on her back, wings spread, and groaned. "That... is getting really old." Ever since their first grudge match years ago, Applejack and Rainbow Dash had held a much more friendly competition during the Running of the Leaves... but as this year's autumn approached, Dash had been plagued by recurring dreams involving her screwing up. It's so stupid... I'm not a dumb filly any more, I don't need to win everything!

Rolling to her feet and shaking out her mane, Dash sighed and trotted through her darkened home, getting a drink from the kitchen. Judging by the moon's position in the sky, it was sometime in the wee hours of the night. Nudging open her kitchen door, she moved out onto the cloud-formed veranda that edged her skyhouse. Cool night air wafted through her wings; she stretched them out, ruffling her feathers, turning to nose a few strays back into place as she contemplated a quick flight through the starry sky, just to shake the last vestiges of the embarrassing dream from her mind.

Striking a pose at the edge of the cloud, Dash prepared to launch herself into the dark, but caught herself at the last minute as she noticed a strange light bobbing along the ground in the distance. "What the hay...?" It actually looked kind of familiar, now that she thought about it, just very out of place as it came toward her through the night... it almost reminded her of...

"Twilight?"

"Rainbow Dash!" Twilight shouted as she came to a panting halt underneath her blue pegasus friend, her horn shining to light her way. "I need you... to do me... a huge favor!"

Dash blinked – what could she need so badly at this hour? – then fluttered down to stand next to the gasping purple unicorn and grinned a little. "What's up, Twi? Isn't it kinda late to be out training for this year's Running?"

Twilight gulped air, her eyes tearing up from the exertion. "Just... give me a minute... to catch my breath."

"Uh, sure thing, take your time."

Dash looked around awkwardly, watching a few scattered clouds slowly cross the moon. A moment later, Twilight coughed and seemed as though she was back to her usual self. "So... you need a favor?"

"Yes." Twilight nodded quickly. "I need you to take me to Canterlot."

"What, you can't wait for the Princess to send a chariot in the morning?"

Twilight looked startled. "How could the Princess send a chariot? I don't even know how she sent me the – oh, you meant Luna."

Dash looked at her friend like she'd had one too many apple fritters before bed. "Who else would I be talking about?"

"Never mind, I can explain on the way, but it's extremely urgent! It can't wait 'til morning."

"Well... if you say so, Twi. Hop on, I'll get you there in ten minutes flat!"

• • •

They sped through the night air, Twilight's teeth chattering a little as she held tight to Rainbow's back, powerful wings pumping on either side of her. "A-aren't y-you freezing up-p h-here?"

Dash looked back over her shoulder, grinning her trademark cocky grin. "Nah... you get used to it." Partly true, at least – most pegasi weren't as bothered by cold as other ponies, though on this particular flight Dash had to admit to herself that having Twilight snuggled up against her was doing an excellent job of keeping the chill away. It had been a while since she'd enjoyed that kind of physical contact with somepony else. In fact, she realized abruptly her last date had been to Applejack's wedding a few years back... not a memory she cared to dwell on. She shifted her hindquarters slightly, settling Twilight into a somewhat more aerodynamic position. "Uh, so... what the hay is so important that we had to get to Canterlot pronto?"

Twilight concentrated for a moment, her horn glowing softly, and Dash felt a cocoon of artificial warmth wrap around her passenger. "Well... I got a letter from the Princess tonight."

The pegasus rolled her eyes. "You get letters from Luna all the time, Twi. So what?"

"It wasn't from Luna, Rainbow."

Dash frowned. "But... you said –" She started a bit and they lost a few feet of altitude, Twilight yelping and burying her face in Dash's mane. "You mean from Princess Celestia?! You got a letter from the Princess? What did she say?"

Looking uneasily toward the ground blurring past them, Twilight said, "Just that she needed my help in her study. Naturally, I'm expecting to find out more when we get there, and you can see why I couldn't wait."

"Totally, this is incredible! Do you have any idea what she needs help with?"

"Well... I'm kind of assuming it has to do with her computational engine..."

"Uh, her what now?"

"Right when she disappeared, she was working on a new invention she thought would make everypony's lives simpler..."

Twilight tried to explain about the work she'd been doing in her basement and Dash listened intently to her friend, even though a fair amount of the terminology sailed right over her head.

"So, let me get this straight... it's like a machine that can think about what you tell it to think about... and you can have it think about all kinds of stuff, like how to do math or what the weather could do..."

"Well, more or less."

"And you have one of these things set up in your basement and it's thinking about Ponyville?"

"It's running a simulation of Ponyville and everything in it. It's surprisingly accurate. In fact, I'm quite impressed with its performance –"

"Yeah, yeah, fine. Here's what I don't get: what does any of that have to do with the Princess disappearing?"

Twilight bit her lip, lost in thought for a moment. "I don't know, Rainbow. I'm hoping to find out."

Dash looked back at her friend, who appeared so lost and – young, all of a sudden. She frowned, determined. "We'll find out, Twilight, I'm sure we will. Look, we're almost there!" She lifted a forehoof and pointed ahead: in the distance, the castle rose up, pale marble glittering in the moonlight. "Now, uh, I don't mean to scare you, but it's been a while since I've carried somepony around like this. The landing might be a little bumpy, is all I'm saying..."

• • •

"Princess, I'm sorry to disturb you like this, but –"

"Nonsense, Twilight, of course you were right to come. Did you bring the letter, by chance?"

Twilight shook her head, looking regretful. "I was so... so shocked and surprised I left it at home."

Luna sighed, but nodded to show she understood.

They were cantering down through the castle, headed for Celestia's secret study, Rainbow Dash trailing behind them. It had been a long time since Dash had been to Canterlot and she'd never been this deep within the castle before. It was kind of creepy, and she picked up her pace, reluctant to be left behind – not that she was afraid.

"All it said was, I need your help. Please come to my study."

"Very cryptic," mused Luna.

"I agree. Naturally, I came as quickly as I could, thanks to Rainbow here."

"Aw, it was no big deal. I couldn't sleep, I was about to go for a little fly anyway."

Luna looked back at her, a slim eyebrow raised. "Bad dreams, Rainbow Dash? I would hope my night is treating my subjects better than that."

"I – uh, your night is just fine, Princess. Er, better than just fine, your night is awesome, it's perfect! Perfectly... awesome. Yeah..." Dash grimaced.

Twilight rolled her eyes, smiling to herself, and Luna grinned. "Don't worry... I'm sure neither I nor my night is insulted. I do apologize for the interruption of your sleep, whether due to nightmares or bringing Twilight to Canterlot."

"Heh, really, it's fine, your Highness."

"Surely after all we've been through you needn't be so formal, Rainbow Dash. You may call me Luna."

"Well... Luna... you can call me Dash, everyone else does."

"Very well, Dash. ...Ah, here we are."

Luna drew to a stop. Twilight, apparently recognizing where they were, halted easily alongside her. Dash managed to catch herself before bumping into either of them, but only just. She looked around with interest and was disappointed by bare stone walls and an unremarkable door set into one side of the hallway. Luna opened the door and they peered in; there was nopony inside.

The three ponies stepped in cautiously, looking around. Dash saw nothing but a workspace and some books. "So... where is she?"

Twilight frowned. "I don't know... maybe..." Her horn lit and she swept it in an arc across the room, gasping when it passed over the bookcase. "Luna! I can feel her!"

Luna turned, her own horn sparking to life, and she gasped as well. "Sister!"

The two ran forward to the bookcase. Feeling slightly out of place, Dash looked on as Twilight and Luna performed more spells, talking excitedly with each other. She gathered that there appeared to be some sort of passageway behind the bookcase that wasn't there before, but they couldn't figure out how to get in. Finally, Twilight noticed something and reached for one of the books – Dash caught the title Simulacra and Simulation, by Boerdrillard – and as she pulled it toward her, a low rumble grew up around them before the bookcase slid to the side, revealing a stone passageway leading even deeper below the castle.

Luna stared. "I had no idea this existed... it's not in the official plans for the castle. Sister, what were you up to...?"

"She must have dug it out herself with magic, and used more magic to seal and cloak the entranceway," Twilight suggested.

Dash looked over their shoulders, down the rough steps, eyeing the wall sconces that had sprung to life when the bookcase had shifted. "Well... shouldn't we check it out?"

Twilight nodded. "Right, of course. Princess?"

"After you, Twilight."

They all headed down the passage single-file, the sound of their hoofsteps echoing around them. Dash felt the air growing even damper as they descended, the humidity making her feathers stick to her fur uncomfortably. Worse, she couldn't help but picture how deep they must be below the ground, how far they must be from the open sky, and she shivered slightly. She tried to keep her unease from showing, since her companions seemed no worse for the wear.

The passage eventually leveled out into a hallway. As they headed for the end, the temperature began rising, the air turning warm and muggy. Dash grimaced and ruffled her wings, lifting them slightly off her body in an effort to stay cool.

The room at the end of the hallway would have seemed fairly cavernous, had it not been packed full of humming boxes like nothing Dash had ever seen before. A few wall sconces flickered to life as they entered, pushing the darkness back, but not by much. As the room became more visible, Twilight bounded to the nearest box and examined it excitedly before turning back to the others.

"These are just like the ones I've built in my basement based on Celestia's notes! This has to be her own computational engine." She glanced around the room, looking bemused. "Hers must be much more powerful... this is several times the size of my own setup."

Dash trotted over to Twilight's side, looking the machine up and down. It was a dull gray, with little lights blinking on one side. Bundles of what looked like rope came out the back, and led to the other machines surrounding them in the gloom.

She nudged Twilight. "What're these for?"

Twilight looked down at the ropes. "Oh, they're cables. They link up multiple smaller computational engines so they can work together, making the system as a whole more powerful." At Dash's blank look, she sighed. "Just... don't touch anything."

Luna was looking around, shock plainly evident on her face. "My sister built all this in her spare time?"

"Well, she worked on it for decades... maybe longer... I was able to do it more quickly because she had laid everything out in her notes."

Luna turned to Twilight. "And you have constructed a similar system in Ponyville?"

"Yes, just smaller."

"Do you think you can operate this one?"

"Probably," Twilight murmured, looking deeper into the room, following some of the ropes – cables, Dash reminded herself. They all seemed to eventually lead back to one box in the center that looked different from the others. There was a cushion in front of it, as if somepony were meant to sit there.

Twilight settled in and inspected the machine, Dash and Luna standing to either side of her. Seeming to sense her presence, a rectangular area on the machine lit up; Dash jumped a little in surprise. "Don't worry," Twilight said. "It's just the display screen, it's... part of how you work with it."

Fascinated, Dash leaned closer, watching numbers that had appeared there count up.

010:01:04:16:52:47, 010:01:04:16:52:48, 010:01:04:16:52:49...

Twilight ignited her horn, activating a few controls on the machine's surface. The numbers disappeared, replaced by luminescent script; Dash couldn't make heads or tails of any of it. "It's the master console... it controls all the other computational engines in the room," Twilight explained as she started working. "It's laid out a little differently than my own at home, but I'm familiar enough with the Princess's organizational style that I should be able to figure out... ah, there we are."

New text appeared and Twilight skimmed it. "This is a list of the most recent commands the Princess entered..." Dash and Luna stared at her. "That is to say, this is a list of the most recent instructions the Princess gave to the machine. If I can figure out what they mean, it should give us a clue as to what happened." She set to work.

Dash watched for a while, but the novelty of seeing Twilight pressing controls on the machine and then things changing on the display in front of her wore off quickly. She looked around; Luna was still gazing intently at what Twilight was doing. Around them, the metal towers of Celestia's computational engine hummed along, all their lights flashing on and off.

Directly behind them, Dash noticed a different-looking machine, quite unlike the boxes. She moved to get a better look at it, stepping carefully over the cables snaking everywhere along the floor.

It appeared to be a large metal cylinder, with several other objects attached to it, on a sturdy stand and base. It was mounted horizontally, with one end pointing back the way she came, toward Twilight at the master console. The end closest to Twilight wasn't solid: there was an opening which contained what appeared to be a highly-polished, perfectly smooth domed jewel. She peered into it and saw her own face reflected back at her, upside-down and foreshortened.

From behind her, she could hear Twilight muttering to herself, and then a sort of excited sound, as though Twilight had figured something out. Dash started to turn back, but the strange device next to her started humming and she jumped away before looking it over uncertainly.

"Hey, Twi..."

"Hold on, Rainbow, I think I've tracked this down."

Dash heard Twilight continuing to press buttons on the console, and then the console beeped. A cool blue light flickered into existence behind the jewel set into the end of the cylinder and Dash stared at it in surprise, watching it begin to glow brighter. She noticed a series of dark rings around what she was slowly beginning to think of as the 'business end' of... whatever it was; the ring farthest from the end of the cylinder was glowing the same shade of blue as the jewel. As she watched, the next ring lit up, and then the next; each ring's ignition coincided with a jump in the intensity of the humming coming from device. She didn't like the noise, it sounded... unnatural, set her teeth on edge. She also didn't like the look of those rings lighting up.

"Twilight..."

"Just a second, Rainbow!"

The pegasus bit her lip and looked back at the two other ponies. Luna sensed her movement and looked back at Dash, then saw the glowing eye of the device; her eyes went wide. "Twilight, perhaps you should stop."

"Done!" Twilight said triumphantly. "Now what is so important?" She turned as she hit a final control. The device's whine immediately jumped in pitch and volume, and the remaining rings began to light faster.

"Twi, move!"

The glow focused itself, projecting a blue circle between Twilight's eyes as she stared back; the device shrieked past hearing.

"Move!"

Time slowed to an agonizing crawl for Dash as she launched herself forward without thought, diving for her egghead friend – Twilight, frozen in shock – Dash flapped, hard – the final ring lit – the jewel blazed blue – Luna cried out, shielded her face with a wing – Dash's body slammed into Twilight's, sending the purple unicorn skidding away –

Dash felt every hair on her body stand on end, a wave of freezing electricity washing over her. Like flying through a thunderhead in a bad storm, she barely had time to think.

Her vision flickered briefly, and then she was alone.

02 Activation

Twilight slid to a halt against the base of one of the computational stacks, groaning as the rough-hewn stone floor scraped her hide. She looked up to scold Dash for her rash behavior but saw nothing – her friend was gone.

"Rainbow?!"

Luna looked horrified. "That device – it fired a blast of energy and she... she dissolved." The princess turned to Twilight. "It would have hit you, had she not intervened. What is this? Some new teleportation spell?"

Twilight pushed herself to her hooves. "Celestia's notes didn't say anything about this... but there's no way Celestia would create something that destroys ponies, so Rainbow must be safe, wherever she is." She moved back to the master console, inspecting the display, mentally retracing her steps. "I had been running through the Princess's commands, re-entering them one at a time to see what they did. There was no indication in her available research that a computational engine could affect the physical world, so I didn't realize... okay, new assumption: any command I enter here could result in an interaction with the physical world in some way, so I need to be more careful in my experimenting with her system."

"Agreed." Luna stepped closer. "Twilight..."

"Yes, Luna?"

"Do you think it's possible that the same thing that happened to Rainbow Dash happened to my sister?"

"I have to think so. And it would be logical to assume they're both in the same place."

"But that place must not be in our world. There is no force that could have prevented Celestia returning to Canterlot."

"So... some sort of alternate plane of existence or reality..."

Luna nodded to the display. "Perhaps she's in there. And now Rainbow Dash as well."

Twilight almost laughed before she caught herself. "Prin– Luna, that... just doesn't make any sense. 'In there' is just a string of ones and zeros, infinitesimal surges of electricity along tiny metal circuits. How could a pony be in there?"

Luna shrugged. "I do not know. This area is as indecipherable to me as unicorn magic is to an earth pony. But I do know two things: all my senses tell me Celestia is here, inside this room, yet I do not see her. And magic takes many forms."

Twilight looked at the strange cylindrical device, still humming slightly, its blue glow fading, and wondered.

• • •

Dash stumbled, hitting the ground and managing to not smash into the master console; she looked around wildly, trying not to panic.

"Twilight?! Luna!"

The room was empty of anypony save herself, but everything else – the console, the towers, the cables – were exactly the same. No... not exactly, she thought, frowning as she willed her heart to stop beating quite so fast. The glowing telltales on each tower, previously a riot of color, were now all a cool white-blue. Everything, in fact, looked a little bluer than normal, a little cooler and crisper.

She spat and worked her mouth uncomfortably, a bitter metallic taste on her tongue. Dash shook herself out and pawed at the ground uneasily, unsure what to do. There was no sign of Twilight or Luna. You don't think...

"Princess Celestia! Are you there?" she shouted, and listened intently. No reply.

Summoning up her courage, she cantered out of the room.

• • •

Dash emerged into the castle proper and looked around warily. Nopony around. Is that weird? She wasn't sure if there would normally be anypony in this area of the castle at this time of day. Er, time of night? It's still pretty early... She started making her way toward the exit – or at least, where she thought the exit was; she hadn't really been paying much attention when they'd all come down this way.

Out of the basement, every surface looked like smooth black marble, polished to a shine. Streaks of blue light ran along the floor at the base of the walls, casting an eerie glow over everything. What the hay happened to me? Everything looks different... Twilight and Luna disappeared... some kind of spell? That panicky feeling rose up in her again and she tried to force it down. She remembered what Twilight told her about the machines in the basement of the library, thinking about Ponyville, filled with simulations of everypony...

Coming around a corner, she almost walked face-first into another pony.

"Oh! Sorry, didn't –"

"Halt," the pony said in an odd voice, deep and sort of garbled. Dash wondered if he was sick. Maybe he was really sick – it could explain the suit he was wearing, or at least why it covered him from head to tailbase. It was jet-black and formfitting, with thicker pieces of some kind of matte-black armor attached at key points; he wore a helmet with a smoked-glass visor that hid his eyes and mane, though his ears and muzzle poked out. It almost reminded her of a Wonderbolts flight suit, except for the armor plates... and the channels of glowing orange all over it, tracing along the pony's body and legs.

"Hey, cool outfit! Are you okay? You sound kinda funny."

"This program has no disc," said the same voice from behind her.

She whirled; an identical pony stood behind her, expressionless, wearing an identical suit. "It's not smart to sneak up on a pony like that, you know," she growled. "You might end up bucked. Now, maybe you ponies can help me out. I think I'm lost, I need to find my way out of here. Can you give me some directions?"

"Another stray. You will come with us."

"Yeah, not happening. Just tell me where –"

"You will come with us." They grabbed her and started taking her down the hall.

"What the hay is this?! Let go of me!" She struggled against them, bucking and twisting, flapping her wings as hard as she could, but they were much, much stronger than they looked – much stronger than her. Dash kept fighting them, until one reached up and smacked her on the back of the head. A burst of power surged through her nervous system, and she speculated in a detached sort of way that this must be what a lightning strike felt like before her eyes rolled up into her head and she was gone.

• • •

She came to in the middle of a circular room, with the distinct impression she'd been dumped there with little regard for her personal well-being. Groaning, the pegasus untangled her limbs and gingerly felt the spot where the guardpony had shocked her; it was tender and there didn't seem to be any lasting damage, though her mind felt like it was packed in fluffy white cumulus. Pushing up to her hooves, Dash shook her head, blinking away the last of the fuzziness, and the room came into focus.

More smooth walls, lit by glowing lines. There were seams running over some portions of the wall, their purpose not immediately apparent. In front of her, two panels set into the wall looked like a good way out of here.

Dash made to run for the doors, but couldn't lift her hooves. She looked down in irritation and saw transparent blue cuffs glowing around the ends of her legs. "Are you kidding me? Hey! Jerks! Get back in here and let me –"

A low hum filled the room and the seams on the walls split, panels sliding away to reveal racks of equipment and four unicorns wearing pure white suits, unarmored, with cool blue lines glowing on them instead of orange. Their manes and tails were pure white and elegantly styled. They stepped out of their alcoves and walked toward her, surrounding her, all moving in unison. Dash was seriously creeped out.

"What are you doing? Get away from me! Somepony had better tell me what's going on around here!"

All four unicorns stopped just shy of her. None of them spoke. Dash looked around at each of them uneasily. "What... uh..."

The lead unicorn's horn ignited. Dash flinched, but nothing happened. She felt an odd sensation around her hooves and looked down. Sleek black material was materializing around them, sparkling into existence, moving up her legs to completely enclose her body.

The other three unicorns lit their horns and pieces of armor floated from the equipment racks, attaching themselves to the bodysuit at strategic points. White-blue lines glowed into being all over her. "Heh, that's... kinda cool, actually..."

The unicorns exchanged glances.

"What?" Dash asked. She turned her head to look back over her body and raised her wings experimentally. The black material had covered them as well, but they seemed to be able to move and function freely. Flapping a few times, she could tell she hadn't lost her lift, though she was still shackled to the floor.

"Your flank had a representation of a... colorful storm on it. Why?"

"You mean my cutie mark? Everypony has a cutie mark. Don't you guys, under your suits?"

The unicorns just stared at her, until one murmured, "You are different."

Before Dash could respond, the lead unicorn spoke. "You shall receive an identity disc. Everything you do or learn will be imprinted on this disc. If you should lose your disc, or if you should fail to follow commands, you shall be subject to immediate deresolution."

Dash started and looked back at the unicorn. That voice...

One of the other unicorns magicked over a strange-looking disc with the middle cut out. She attached it to a port on Dash's flank, turning it to lock it in place. It glowed, and Dash twitched. Something felt... funny. The back of her neck tickled for a few seconds.

"Mirroring complete. Disc activated and synchronized. Proceed to games."

"Games?"

The four unicorns retreated to their alcoves. Dash tried to follow, but she was still stuck to the floor. "Wait! Rarity...?"

The lead unicorn gazed at her. "I am Jewel."

"Jewel?" She could have sworn... Sure, her mane was different, but the way she moved, the way she talked...

The wall panels began to slide closed. Dash called out, "What am I supposed to do?"

Jewel grinned at her just before her panel sealed shut, her ice-blue eyes twinkling.

"Survive, darling."

• • •

Dash followed the luminous symbols on the walls; a different wall panel had slid open and indicators had lit up, guiding her down a hallway. She reached the end and stopped: it was a dead end. She frowned and turned around, looking back the way she came, when without warning the floor jerked and sped upward, taking her with it. She tensed into a crouch, watching as the walls around her blurred. Be cool, Dash... just an elevator.

The floor slowed as it reached the top and smoothly clicked into place at the surface, with no apparent seam. Dash looked around, almost overwhelmed by the roar coming from every direction – what sounded to her like the roar of thousands of ponies eager for a fight.

She was in the middle of a vast arena. There were other ponies with her, wearing similar black suits with glowing blue lines, all standing at attention as though they were waiting for something. The ground level of the arena was broken up into different sections, some of which she recognized, some of which she didn't. Horseshoe pits... tug-of-war ropes... high strikers... looks like another Iron Pony competition to me.

The ground level was surrounded by stands, and the stands were filled with thousands, maybe hundreds of thousands of ponies, all wearing suits that glimmered either blue or orange in the distance, all cheering and stomping the ground. They aren't eager for a fight... they're eager to see some competition! At one end of the coliseum, there was a high tower; she thought she could make out some movement at the top.

Dash looked up, glad to finally be out of the castle and back under the sky... but she paused at the strangeness of this one. Dark clouds roiled above her, white-blue lightning cracking between them – the sky of an angry goddess. Even allowing for the oppressive clouds, she got the sense from the quality of light that it was still nighttime. Wait, 'still'...? With a start, Dash realized it had been less than an hour since she had been with Twilight and Luna in the other castle. She felt a sudden surge of longing and homesickness: she already missed Twilight and her friends, missed Ponyville. What the hay have I gotten myself into?

A calm voice reverberated through the arena. "All combatants, prepare for Pillar Weave."

The crowd went even wilder, stomping their hooves and chanting, "Pillar Weave, Pillar Weave!"

On Dash's left, there was an area she had more or less ignored, as it seemed to be empty. Now she watched with interest as the border of the area lit up and glowing blue pillars extended themselves out of the ground in a straight line. Two lines shimmered to life on the ground at the beginning and end of the line of pillars, perpendicular to them. Looks familiar enough.

Dash found herself caught in the press of ponies moving toward the first line. "Hey, watch it!" she said indignantly, but nopony reacted. They formed a queue, and she ended up in the third spot. A scoreboard materialized, suspended in the air over the course with no apparent supports, with a line for each combatant's identifier and time.

"Combatant One. Pillar Weave. Begin."

The first pony in line, a unicorn mare, tensed, leaned forward, and took off. As she passed over the first line, it flashed, and the first scoreboard entry, the one labeled Combatant 1, started counting up. When the pony reached the second line, it flashed again and the counter stopped.

"Combatant One. Pillar Weave. Twenty-one point three seconds." 21.3 flashed on the board as the crowd stomped their hooves.

"Oh, please. I could beat these ponies in my sleep," Dash muttered as the second in line, a pegasus colt, started their run. "I wonder how bad they ding you for nudging a pillar..."

As he neared the end, one of the colt's wings extended a feather too far and brushed against a pillar. Dash jumped at his agonized scream, watching in horror as he shattered, falling apart into a thousand tiny blocks that scattered on the ground before dissolving into nothingness.

"Combatant Two. Pillar Weave. Disqualification." An X flashed on the board.

Dash gulped. That's different.

"Combatant Three. Pillar Weave. Begin."

Dash took her mark and launched herself forward, making a point to keep her wings tucked tightly against her sides, her trademark rainbow trail blazing out behind her as she sped between the pillars.

• • •

High above the arena, a pegasus mare wearing a black bodysuit, cloak and helmet gazed out idly over the combatants and spectators as she lounged on her private observation deck. It was the highest point in the entire coliseum. The orange telltales on her outfit flared as she turned at the sound of the entrance sliding open. Another pegasus mare in an orange-striped suit entered.

"Um... no unusual activity. Security sweeps and patrols have been intensified... I hope that's okay?"

"Good," said the first mare. Her voice was deep and distorted by the helmet. She turned back to the arena and smirked as a pegasus colt derezzed after letting himself brush one of the pillars on the weave course. "Idiot. I tell you, Shy, I could beat any of these programs in my sleep."

"I'm... sure you could, ma'am. W-was there anything else?"

"Nah, not right now. Go hide yourself in a corner somewhere."

"Um, yes, ma'am." Shy meekly backed toward the exit.

Below them, the next combatant started their run, a spectrum of light trailing behind her. The mare sat up, staring at the sudden burst of color as the combatant crossed the finish line.

"Combatant Three. Pillar Weave. Fourteen point seven seconds." Below them, the crowd hesitated in surprise before breaking into raucous cheers.

The mare turned. "Shy! Get back here. Who is that?"

"Oh, um, I don't know." Shy nosed a wall panel that lit at her touch; biographical information on the combatants on the field flashed past. The screen titled Combatant Three was filled with question marks. "No data, ma'am... I don't understand how –"

"Well?" the mare prompted impatiently.

Shy squeaked and nosed another control, then spoke. "Combatant Three, identify yourself... if you wouldn't mind." The mare rolled her eyes.

• • •

Dash grinned, looking out at the assembled ponies cheering her. Showed them, she thought triumphantly. Fifteen seconds wasn't bad, but she could do better. She chalked the relatively marginal showing up to the strange situation. If these ponies love athletes, I bet I could get to like it here... wherever here is.

A voice echoed through the arena. Not the announcer, somepony else. Another familiar voice. "Combatant Three, identify yourself... if you wouldn't mind."

Dash looked around, confused. Where is that coming from?

A harsher voice: "Identify!"

Dash frowned and spoke to the air. "I'm Rainbow Dash, from Ponyville." A hush fell over the crowd, murmurs replacing cheers. "What? You guys heard of me?"

The first combatant, the unicorn mare, had been standing nearby, looking generally impressed by Dash's performance. Now she looked tense and afraid, ready to back away.

"What's the big deal?" Dash asked her. "Where are you from?"

The unicorn made as if to speak, but nothing came out. She looked behind Dash, and Dash turned. An armored pegasus stood behind her, orange suit stripes burning menacingly. She could see nothing of the mare's face, completely encased in a smooth black helmet that reflected Dash's apprehensive expression right back at her.

"Combatant Four. Pillar Weave. Begin," said the calm announcer's voice. "Combatant Three. Accompany Cracken."

Dash groaned. The guardsmare moved to grab her and she flapped once, kicking herself back out of reach. "Chill out! I'll come quiet, no need to get rough."

• • •

She was taken out of the center of the arena, under the stands, spectators leaning over the railings to watch them go. Two more armored pegasi met them at the edge of the field and took the lead, the pony the announcer had called Cracken bringing up the rear. Cracken's name didn't strike Dash as the sort of name a friendly pony would go by; she glanced back over her shoulder, watching the other pegasus. Dash couldn't help but think there was something familiar about this pony too... something. She ran though the names of the pegasi she knew in Ponyville as they walked, but couldn't put her hoof on it.

They came to a door that hissed open at their approach and stepped through. Another elevator ride took them to the top of a tower – it was a long ride, so she figured it was the one she'd seen earlier. More doors opened for them and the guards marched through, Dash following.

The room's walls were made up of more of the smooth black material she'd seen elsewhere and lit by glowing conduits of light running up and down the walls and along the ceiling. Big bay windows on the wall across from her looked out over the arena. She saw another pony make their run down the weave course, and heard the announcer state their identity and time, but it was muffled and distant.

A pegasus mare, wearing a cloak over her bodysuit and a glossy, opaque helmet similar to Cracken's, was standing in front of the windows, her back to Dash, her cloak covering her tail. The two guardsponies moved to either side of the cloaked mare and stood at attention, their hooves snapping on the floor. Cracken took up a position behind Dash, just off to one side, a little more relaxed than the other guards, though Dash got the sense Cracken would be the one to watch out for in a fight.

Nopony moved for what seemed like a long time.

"Where am I?" Dash finally asked, a hint of frustrated impatience in her voice.

The cloaked mare turned, faced Dash, didn't say anything.

"Who are you?!" demanded Dash, stomping a forehoof.

There was a moment of silence. Then –

The cloaked mare's helmet hummed, split along hidden seams, and folded itself back behind the mare's head, letting a lock of multicolored mane fall across her forehead.

Dash gaped at her own face smirking back at her.

03 Recursion

The two rainbow-maned, blue-coated pegasi stared at each other. Dash couldn't believe what she was seeing. She'd always felt she was unique: not just the tripe parents fed their foals about "everypony being special in their own way", but because ponies with naturally many-colored manes were fairly rare, and she had never met another pony that shared the same shades that were her namesake. Even worse... even worse, this pony was her – the same face, the same coat, the same rose-hued eyes she saw every morning in the mirror.

A wave of vertigo swept over her, as though she'd been riding a thermal a mile up and lost it suddenly, plummeting down; she scrambled to regain control, to stay calm, to figure out what the hay was going on.

This wasn't her. This... other self looked grimmer than she ever had: there was a hard set to her jaw, a tightness around the eyes, and the eyes themselves, well... she knew she'd never looked so cold and calculating. There was darkness there, and she didn't like what it did to her face.

"Rainbow Dash," said the cloaked mare, and Dash shuddered with unease at the sight and sound of her own voice coming from another pony who looked exactly like her, and moved exactly like her – for the other Dash had stepped forward with an easy, athletic grace, sauntering toward her, looking her up and down. "I never thought I'd meet you in the flesh, as it were. How did you get in here?"

"I... Twilight found Celestia's thinking machine in the basement, and turned it on, and..."

The other Dash circled her. "Ohh, so it's just you?" she said speculatively.

"Yeah..." Dash found herself feeling more alone than ever, and fought to keep the fear away. Her friends flashed in front of her mind's eye before settling on the lavender unicorn that had gotten her into this mess. Twilight could be a little scatterbrained, but she always knew what to do; having her here would be so reassuring...

"Just you," mused the other Dash. She gestured to Cracken. "Disc."

Cracken stepped forward, removed the identity disc from Dash's flank, and gave it to the other Dash.

"Who are you?" Dash asked, finding herself dreading the answer. If they shared a name as well, she didn't know if she'd be able to handle it.

The other Dash glanced back at her, a dark little grin quirking her lips. "Call me RBD." She held up Dash's disc, eyeing it for a moment. "Let's have a look." A stream of light and color sprang to life above the disc and RBD watched intently. Dash peered over her shoulder and saw a torrent of images of her own life: her time in flight school, her first sonic rainboom, running the weather patrol in Ponyville, her friends. A flash of angry heat passed through her. Those are my memories! That's private. Before she could do anything, the playback ended and RBD tossed the disc back to Cracken, who reattached it to Dash's flank with a click and stepped back to her original position smartly.

RBD appeared lost in thought for a moment. "Hmm. I expected more."

"What's that supposed to mean?" Dash asked indignantly.

A glowing hoof waved away her question. "Now... since you're here, I have to decide what to do with you. I suppose you could join me. It's not often a program can be in two places at once, that could be... useful."

Dash frowned, looking around. "Join you? You run this place? Where's Princess Celestia?"

An ugly look crossed her double's face. "Ah, yes. The creator. She's... indisposed. I'm the top pony here. And I'm offering you the chance to be a part of something impressive, be my right-hoof lieutenant. It's obvious you don't have much going on back home."

"I have plenty going on! My friends, my job –"

"You arrange clouds, taking orders from somepony else," RBD said cuttingly. "You work a dead-end job in a backwater town, far from the glory and admiration you so obviously want. I can give you these things. Here, all will know your name, all will look upon you and marvel at your speed and power. You could lead the Guard, my most elite and trusted pegasi warriors. The... Wonderbolts, I believe they're called?... have nothing on them."

Dash looked around her at the other ponies in the room: motionless Cracken and the members of the Guard that had led her here, one cowering in the corner. She needed a distraction, she needed to keep her cool, she needed to keep the burning resentment and despair RBD's words had awoken within her from overwhelming her. So I lead the Ponyville weather patrol instead of the Wonderbolts, so what? I'm happy in Ponyville, happy with my friends, happy with –

"Well?" said RBD impatiently. "Will you join me or not?"

"No," Dash said quietly. "I like my life. I want to go back to it. Now. You tell me how to get out of here, and I'm gone. My... friends are waiting for me."

RBD stared at her, and she stared back, unwavering.

"Your friends? Applejack, Fluttershy –"

A meep came from the pegasus in the corner. Dash started a bit but immediately snapped her attention back to RBD, who had ignored it. Fluttershy?

"– Rarity, Pinkie Pie... Twilight Sparkle."

Dash stiffened at the sound of her own voice saying her friend's name in such a distasteful tone.

"Yes... Twilight Sparkle. The know-it-all egghead. The idiot who spends all her time locked away in her precious library, snout in a book, ignoring you unless she needs your help with something. What possible interest could you have in returning to that?"

Dash gritted her teeth. "Don't talk about her that way."

"Why not? She's spent years ignoring you; you can't deny that. Now it's your turn. Ignore her, ignore all of them and stay here, and live like a goddess."

"No," spat Dash.

RBD looked at her, unamused. "Last chance, Rainbow Dash."

"Did I stutter? I'm not staying here, I'm going – hey, get your hooves off me!" The pegasi Guards had come up to her, grabbed her, started dragging her out of the room. "Where are you taking me?"

RBD moved away, looking back out over the arena, her back to the others. Dash struggled against the Guards, thinking fast.

"RBD!" shouted Dash. "Where is Celestia? What did you do to her?"

RBD turned, glaring at Dash with such hateful intensity she went slack in surprise for a moment, unaware her face could look so cruel, unhappy to learn that it could.

"The same thing I'm going to do to you, user."

• • •

They took her back to the arena, which had been cleared of the other combatants and reconfigured in her absence. The various Iron Pony-style competition areas had disappeared, leaving behind a smooth glassy surface. Looking up, Dash saw the same roiling, stormy sky – but frowned when she saw less of it than before, and less of it by the second, for the arena was closing itself off, a ceiling materializing above them, sealing them in. Trapped.

The guardsponies released her and she stood alone in front of the stands, thousands of ponies pushing and jeering above her, eager for a look at the newcomer. She glared back at them, striking a defiant pose, and quickly scanned the interior of the now-enclosed coliseum, looking for any possible way out but finding none.

Behind her, she heard this place's version of Fluttershy begin speaking, at the same time hearing the timid voice boom from the arena's loudspeakers.

"Greetings, programs. What an... um... occasion, we have here before us. That is, because, we do indeed have in our midst a... user..."

She trailed off as Dash turned to look at her and squeaked a little before she continued, a little more strongly, pointing a hoof at Dash: "A user."

The crowd shouted and jeered, a roar of disapproval that crashed over Dash, almost making her wince at the force of it.

"So... what should we do? What does this... user... deserve? Maybe... um... the challenge of the Grid?"

Another roar, this one of approval and anticipation, of ponies wanting to see an enemy destroyed and secure in the knowledge they'll soon get their wish.

"And... who better to battle this... singular opponent? Perhaps someprogram who has some... um... experience... in these matters?" More approval from the crowd. Dash didn't like where this was heading. She readied herself, tensed up, wishing she knew what she was readying herself for.

"Your liberator... your luminary... your l-leader... the one who vanquished the tyranny of the user so many cycles before..."

An explosion of light from above made everyone look up. Dash saw the remnants of a firework sizzle out of existence and RBD come soaring out of it, banking, spiraling down toward the ground, moving faster and faster.

"Arrr Beee Deee!"

At the last second she flared her wings, braking, and slammed into the ground, sticking the landing perfectly, sending a wave of energy rippling through the strange glassy material they stood on. The crowd erupted, everyprogram leaping to their feet and calling, cheering, stamping their hooves. RBD reared up on her hind legs, shadowboxing, spreading her wings to full extension, reveling in their adulation. She fell back to all fours and stalked over to Dash, swishing her tail, flicking Dash in the face as she walked past.

"I've dreamed of this for a long time," RBD murmured in her ear, coming back around to face off with Dash, staring her down.

"Dreamed of what?" Dash snapped, but Fluttershy's double was approaching, balancing a tray with two bracelets on her back. She drew up between them and RBD reached out, taking one of the matte black devices and fitting it around her hoof with the detached air of somepony who's done this a thousand times; small telltales glowed to life on it. Dash reached out for the second, hesitating when she saw the bearer balk at the approach of her hoof.

"What's your name?" she asked, trying to inject a note of kindness in her voice, not sure if it was audible through the gruff bravado she felt obliged to keep there in this situation.

"I'm... I'm Shy," murmured the other pegasus.

Dash started to roll her eyes but caught herself. "I know you're shy, we're frie– I mean... I have a friend a lot like you, back home."

"Oh, no," Shy said, "that's my name. I'm Shy."

"Oh... right." Dash reached out again and took the band from Shy's back, who didn't recoil this time.

"Y-you... have a f-friend... like me?"

"Oh, yeah. She's my oldest friend, actually. We've known each other since I was just a little filly."

Shy bit her lip and looked ready to ask another question, but RBD swatted at her haunch; she yelped and galloped toward the stands. She blew past Cracken, who was standing in the entrance to the arena. Dash had the distinct impression Cracken was watching her.

"Enough chit-chat," RBD growled. "Game on!" She leapt and Dash ducked, though Dash realized belatedly she had taken off and was soaring over her; in slow motion, Dash looked up to see RBD touch a control on the band around her forehoof. Glowing lines of energy pulsed up her forelegs, snaking around the shimmering outline that was forming out of nothing: individual components coalesced from pure light into physical form and snapped together almost faster than she could process. Less than a second after RBD launched herself forward, a sleek black pack sat between her wings, and another touch of her forehoof triggered a burst of heat and light from shaped vents at the back of it, kicking her forward through the air at breathtaking speed.

"We've got no chance, user." A garbled voice came from behind her and she whirled, seeing four earth ponies rise up level with her, each with a bracelet around a foreleg. "They're all pegasi, and we don't have wings – we can't maneuver like they can." At her frown, the pony pointed up with his hoof, and she saw four pegasi Guards blast out into the arena from RBD's tower. They trailed ribbons of burning orange light that didn't dissipate behind them, looking like shimmering stained glass suspended in midair.

Dash heard hooves and turned back from the sky to her new friends, but they were already sprinting away, and one by one they touched the control on their bands and their packs lifted them away from the ground. She could tell immediately they wouldn't be as agile in the air as a pegasus, and there was something almost charmingly ungainly about an earth pony with its legs tucked under itself banking into a turn in midair. She shook herself out, unfurled her wings, and grinned.

"Okay, this I can do."

Dash exploded straight up, flapping hard once, twice, before touching the activation stud on her own band, seeing a smoked glass helmet unfold itself into place around her head, feeling the pack materialize on her back, feeling the kick as it activated, the thrust carrying her into the sky, like nothing she'd ever felt before. The effortlessness of it was exhilarating, the sense of speed and power as she cut through the air faster than she had in years.

The coliseum's new ceiling was coming up fast; it was clear, the same strange glasslike material as the floor, and she could see the sky beyond it, though somehow it wasn't all that reassuring. She twitched a wing and banked to the right, spinning out toward the center of the arena, startled by the beauty she saw there.

Everypony had ribbons of light trailing from them: the four Guards with their orange, led by RBD, whose ribbon was deeper, almost bloodred, and her four squadmates a delicate blue. As they twisted and dove around one another, the ribbons swirled and spun, tracing their flight paths, forming an enchanting crystal sculpture. She arced gently toward it, taking it in, feeling more at peace than she had since arriving in this dark place, loving the wind in her mane and tail, the rush of the air over her wings, even the hum of the device strapped to her back was somehow comforting...

One of the blue ribbons of light ahead of her flickered and died; the abrupt disappearance snapped her out of her trance, and she peered into the crystalline construct, frowning. She saw an impact mark on one of the orange barriers, a cracked star pattern, like she'd seen when a bird flew full-force into a windowpane. The shattered remnants of the earth pony who'd hit it rained to the ground, dissolving completely as they hit. She heard a cheer from the crowd, saw the exultant looks the flying Guards exchanged, and her eyes narrowed. Get your head in the game, Dash. This isn't some leisurely drift through the night sky, this is serious. Now get down there and show them how it's done! She hit the only other control on her legband and looked back, watching her own barrier flare to life behind her. She was grimly pleased to see that unlike the others' single-color ribbons, her was imbued with her very own rainbow dash, that prismatic streak of light that trailed behind her when she was moving at speed.

Dash tucked her wings in and dove, spinning into the outer layer of crisscrossing ribbons, blowing past one of the Guards like he was standing still. She smirked at his shout of surprise, swooping in front of him, hearing him get cut off as he smashed into her barrier at full speed, bursting into thousands of pieces that chimed and tinkled as they bounced down through the ribbons.

The Guard's ribbon disappeared as he did, opening a new path toward the other side of the translucent maze, and she sped through it, looking around, assessing the situation. While she'd dealt with the Guard, another of her teammates had been lost, and the two remaining were retreating to the outer edges of the arena, RBD and her minions in hot pursuit. She kicked up and over the central core their ribbons formed and blasted toward them, overtaking the trailing Guard from above. He looked up at her and she waved down at him before furling her wings and cutting the power to her pack's jet, dropping like a stone across his flight path, trailing rainbow death. He screamed and covered his face with his forelegs but it afforded little protection: one more out of the game.

Dash reignited her thruster and sped forward, coming up between the two remaining Guards, who gave her one look and immediately banked for each other, trying to sandwich her, but she put on a burst of speed and whipped past them; they skidded along either side of her ribbon for a moment before righting themselves and taking after her.

Ahead, she watched as RBD did much the same to the flying earth ponies, but when they dove together in an attempt to pincer her, she pushed ahead and cut right, catching one of them in the curve of her barrier, his anguished cry ending abruptly. Dash gritted her teeth and strained forward, catching up to her last squadmate, the two pegasi Guards trailing her, RBD banking in a long loop around the arena.

"Come on!" shouted Dash. "We've got to work together!"

The earth pony looked behind himself, then over at Dash and nodded. Dash looked back as well, gauging the distance from their pursuers, and sideslipped a little closer to her partner. Their barriers were corralling the two Guards behind and between them, though the idiots didn't seem to have realized that yet. Dash gestured to the earth pony and they both slowed imperceptibly, allowing the Guards to catch up... but also decreasing the amount of time they'd have to react to any maneuvers.

"Steady... steady... now!" Dash and her squadmate swerved toward each other, locking in a midair hug and corkscrewing around; Dash looked down between their bodies to see their ribbons spin into an impassable cone of light, saw the shocked expressions on the Guards' faces just before they both vaporized against the glassy barriers.

The two survivors broke apart and pulled right, skimming along the outer wall of the coliseum above the crowd. Dash reached out a foreleg and the earth pony bumped it with his own, grinning widely, riding a sweet wave of adrenaline. "That's what I'm talking about! Now let's get out there and show that madmare how it's done!"

Dash pivoted so her belly faced the wall and kicked, her strong back legs instantly adjusting her course, sending her shooting back out toward the center of the arena. A quick glance back told her that her wingmate had managed to come around on her tail. Not bad for an earth pony, she mused. Looking ahead, she found the arena much changed: with seven ponies out of the game, most of the light ribbons were gone, opening up more maneuvering room but making it harder for her to trap RBD in a bad spot. Speaking of... where the hay is she? Dash darted her gaze around frantically, following the trail of the bloodred ribbon slicing across the sky.

It looped through the center of the arena before coming up and over behind them. Dash gasped and looked left just in time to see RBD streak at her wingmate from above, savagely punching his pack; it exploded in a dazzling burst of energy and the earth pony fell out of the sky, howling in terror. RBD glanced over at Dash, a wicked smirk on her face. Dash growled and shut off her own pack, pointed herself at the plummeting earth pony then reignited, shooting towards him at breakneck speed.

He saw her coming for him and spread his legs, trying to increase his drag to slow his fall. She stretched out a foreleg, reaching for him... he reached back, and she could see the fear in his eyes through his visor... their hooves were almost touching, the ground was coming up fast...

Something slammed into her from the side, knocking her away from him. Instinctively, she tucked in her wings and braced just as she hit the ground, bouncing and rolling. As she tumbled, she felt the weight of her pack dissolve away. She scrabbled to a halt and looked back, seeing the shards of her last teammate melt away, as RBD banked up and around, coming back towards Dash to finish the job.

Dash growled and punched at her legband, but nothing happened – looking down, she saw its telltales flicker and fade before it dissolved into light. She looked back – RBD was streaking toward her, a vicious grin curling her lips – she braced herself, grimacing in pain, frustration, anger – not like this, she thought, it wasn't supposed to be like this!

A burst of pure white light blinded her; when her vision cleared, another pony stood next to her, and RBD was arcing away erratically, her forelegs covering her visor. Dash gaped.

"Grab my tail!"

Dash stared at the newcomer. A unicorn, in shades of purple. "Twilight?"

"Grab on!"

Dash clamped her teeth on the mare's tailbase, and white-hot light consumed her.

• • •

"Okay. Objectives: one, determine which of the commands I entered is specifically responsible for... dematerializing Rainbow Dash; two, determine if any other available commands are capable of interacting with the physical world, in the interest of our safety; three, determine where Rainbow Dash is now, which should hopefully lead to four, determine where Princess Celestia is now; five, determine how to get them back. Simple," said Twilight.

"Is it?" asked Luna.

"Well... probably. Hopefully?"

"Then let us begin."

04 Loading

Dash stumbled – that's getting old – as the ground changed from slick smoothness to rocky unevenness beneath her hooves. She tried to look around, but it was pitch black.

"Twilight?"

Lavender light sparked up to her left, illuminating a horn the same shade, and she shielded her eyes; a moment later warm yellow light filled the room. Room might be the wrong word, Dash thought as she blinked, looking around.

She was standing in a chamber hewn from blue-black rock, the surfaces rough, a contrast to the sleek surroundings of the Grid. Beside her stood a unicorn wrapped in a skintight jumpsuit not unlike her own, with channels of pale yellow tracing over her body that reminded Dash of sunlight.

"I'm afraid not, Rainbow Dash... but I can understand your confusion." Purple eyes twinkled back at her; Dash stared, her mouth hanging open. Despite the coloration, this was definitely not her Twilight. The outfit was one thing, but the rakishly-styled haircut was quite another. Both her mane and tail were cropped short, though they maintained her usual straight-angled cuts.

"Uhh..." Dash found her voice. "Yeah, you're not Twilight. So... who are you? And how do you know who I am?"

"My name is Spark. And I know a great deal about the great Rainbow Dash! Celestia's told me all about you and your frie–"

"Celestia!? Is she here? Is she okay!?"

Spark grinned. "Yes, she's perfectly fine, if a bit lonely. I guess I'm not always the best company. And I'll take you to her now, she'll be really excited to see you!"

Dash allowed herself to be led off through a short tunnel cut out of the rockface. She was silent at first, trying to come to grips with her rapid-fire reversal of fortune and mildly distracted by Spark's too-short tail bobbing in front of her. Finally, she said, "You're not Twilight. I've already met not-Rarity, not-Fluttershy, and not... me. So what are you?"

They'd reached the end of the tunnel and come to rest on a smooth platform. As Spark turned to face her, the platform lit up and began to rise, taking them with it. Dash looked up and saw darkness stretching away above them.

"I'm a program. I was written by Celestia, based on your friend, as were the other familiar programs you've met."

"Yeah... Twilight sorta explained this stuff before, but... I didn't really get it. What exactly is a program?"

"At the most basic level, I'm simply a sequence of instructions designed to be carried out by Celestia's computational engine. I'm admittedly a fairly complicated sequence of instructions, covering everything from how I look and move, to how I'm allowed to interact with the world around me, to how I sound when I speak and how I process information – that is to say, how I think."

Dash considered this. "That's weird," she announced before tentatively prodding Spark's side. "You don't feel like a list of instructions."

"That's because one of those instructions is to make me feel like a real pony," Spark said cheerfully.

Dash sighed. "Of course it is. So am I a list-of-whatever now that I'm in here too?"

"No," Spark said thoughtfully. "You're something else entirely. You're a user – a real flesh-and-blood pony, represented within the virtual reality interface by very powerful magic that I don't fully understand."

"Now I know you're not Twilight," Dash laughed. "There's no magic she doesn't understand."

Spark looked indignant. "I doubt your Twilight would either! Only Celestia is capable of manipulating and maintaining the necessary spell matrix. She's taught me the theory behind it, but I haven't yet figured out how to actually execute it. It can be quite draining for her; she spends a lot of time in meditation to keep her strength up."

"Huh." Dash turned this over in her mind. She'd never seen Celestia look tired... well, there was that one time Chrysalis had knocked her down... She opened her mouth to ask a question, but Spark shushed her and she managed to keep herself from bristling impatiently.

"We're almost there. She's meditating now, so keep quiet while I rouse her." Dash nodded, and the platform clicked into place. They had arrived in a large room with polished floors that matched the platform – like before, she couldn't even locate the seam – but rough blue-black walls, like the tunnel they'd come from.

There was furniture scattered throughout the room, low-slung sofas and lounges and tables, and bookcases along some of the walls. The far wall wasn't a wall at all, but a great wide window looking out over the darkened landscape. Dash thought she could see Canterlot off in the distance.

In the center of the room sat a great shape, softly glowing in a mystical field of light. It almost looked like slow-falling stars, or raindrops made of energy. The shape itself was dark, roughly twice Dash's height, and she almost wouldn't have recognized her, except she'd known to expect her: gone were the crown and jewels of office, replaced by a flowing black robe with one or two streaks of light tracing its curves, and her usually rippling mane hung limp on her neck. Dash realized she was seeing a different Celestia than she'd been used to in her youth. Celestia was cloaked, secretive... in hiding.

She stayed where she was as Spark trotted over to the silent form of the princess. Her large eyes were closed, and their eyelids flickered gently when Spark bent her mouth to a great white ear and murmured, "Celestia, we have a visitor."

Eyes still closed, Celestia smiled ruefully as she shifted and sat up, rolling her neck, shaking out each leg. "That's a new one, Spark. Very funny; your studies of humor are coming along nicely."

"She's, uh... she's not joking, Your Highness."

Celestia froze. She turned to face Dash, and opened her deep magenta eyes. Spark bit her lip and stood off to the side as the two flesh-and-blood ponies stared at each other.

"Rainbow... Dash."

A few hours ago, Dash had been sure she'd never hear her name in that voice again. She was surprised by how anticlimactic it felt: ten years since she'd last seen her princess, and they were just standing there looking at each other. She remembered herself and dropped her front half into a bow; her suit squeaked in protest. "Princess Celes–"

She felt herself swept up by forelegs much larger and stronger than hers, and found her face pressed into a vibrant multicolored mane that was not her own. "Rainbow Dash!" the princess half-choked, and they fell to the floor, Dash frantically trying to think of something to say or do as the Goddess of the Sun wept into her mane. She looked to Spark for help and was further surprised by a wistful smile on the program's face. "It is you – not a program, not a simulacrum, not a fevered dream! I can tell." She pulled back slightly, staring into Dash's eyes. "Do you know you are the first real pony, other than me, to enter the system?"

"I, uh... I guess it's an honor, Prince–"

"Call me Celestia, please," the princess cut her off. She seemed to come back to herself slightly, looking down at the two of them huddled up together on the floor. "Forgive me. It has been... it has been a very long time since I have seen anypony I did not personally create."

Celestia stepped back, her robes falling into place, and Dash pushed herself to her hooves. "Ten years is a long time, Prin– Celestia. We've all missed you."

Dash was shocked to see a haunted look flit through her princess's eyes. "Ten years is a long time, my little pony. A thousand years, a much longer time."

"What?"

Spark came up beside Celestia. "She means, Rainbow Dash, that time passes more quickly within the simulation than it does outside it. By a factor of one hundred, to be precise."

Dash gaped. "You've been trapped in here for a thousand years?"

Celestia nodded. "When did you arrive in-system, Rainbow Dash?"

"I dunno, an hour or two?"

"Then only a minute or so has passed in the real world." Before Dash could ponder the implications of this, she continued. "I must know, Miss Dash – well, I must know a great many things, and truth be told I am having difficulty ordering my thoughts, but most importantly: how did you come to be here?"

"Look, both of you, just call me Dash. And it was kind of an accident. I'd given Twilight a ride to Canterlot after she got your letter, and –"

"My letter?"

"Yeah, you know, the one you sent to Twilight, asking her for help?"

"My letter... Of course. Please, do continue."

Dash frowned, but kept going. "So anyway, I was tagging along with Twilight and Princess Luna when they figured out how to open your secret bookcase thingy and get into your hidden room, and Twilight started messing around with your master console or whatever, and then this other machine almost zapped her but I pushed her out of the way and got I zapped instead! Next thing I know, I'm in a weird version of the castle and everything's different."

"I expect you were then captured by a Black Guard patrol and taken to the Challenge Grid."

"She was about to be derezzed by RBD, but I intervened," Spark chimed in.

"Well done, my student. But only programs are subject to deresolution; the correct term for a user is 'death'."

"Noted."

"Wait – I really would have died? Like for real?"

Celestia pursed her lips. "Yes. Your consciousness would be transferred to temporary storage for eventual permanent deletion, and your body would be ejected from the matter storage matrix – that is to say, it would reappear in the real world."

Dash scrunched up her face. "That seems like a really stupid way to do it... uh, no offense, Prin– Celestia."

The princess laughed lightly. "I agree, Dash. I didn't have a chance to write all the necessary subroutines for handling that particular situation before I became trapped inside, and it's not possible to modify the simulation's executable code from within."

"Uh... right."

"Celestia," said Spark, and Dash thought for a moment how strange it was to hear Twilight address the princess so directly.

"Yes, my student?"

"You sent a message to the outside world without mentioning it?"

Celestia's face grew dark and troubled. "No, I did not."

Dash started. "Hey! Yes you did!"

Celestia turned and strode slowly to the window. Spark followed and Dash hurried to catch up, and was surprised to see there wasn't a window at all: the room was completely open to the outside world. She looked out and, despite the lack of illumination, recognized the view. "We're in Smoky Mountain, right? Where that dragon was trying to take a nap, and you sent us to get rid of him?"

The ghost of a smile passed over Celestia's muzzle. "Yes. It seemed the safest place to lay low. Who would ever think to look for the Creator in an unremarkable cavern, deep within a mountain chain?"

Dash muttered, "I still don't really get why you sent us to do that. You're Princess Celestia, you could have just made him leave."

Celestia arched an eyebrow. "Is that the world you want to live in, Dash? One where all your problems are solved by your princess, where you must never learn nor grow, where you make no decisions of your own?"

"Uh... I guess not."

"No. Little good comes of trying to do everything for everypony. Dictatorship, no matter how benevolent, rarely ends well, and in the meantime it makes everypony's lives very... boring." Spark looked up at Celestia with an unreadable expression, and Dash suddenly felt uncomfortable.

"I'm sorry, Pri– Celestia. I've – we've all – had good lives."

Celestia turned, looked down at Dash, smiled. "I am glad to hear it. And I would be glad to hear more. Are you hungry?"

Dash paused to think. "I... I guess so, yeah. Does that even make sense?"

Celestia laughed again. "Of course; you're still a pony. Come, I'll prepare something for us while you tell us of Equestria... the real Equestria."

• • •

While Celestia magicked up raw ingredients and Spark acted as assistant chef, Dash told them about life back home since the princess had disappeared. She regaled them with tales of Rarity's expanding business interests, Applejack's reluctant acceptance of a certain small degree of automation at the farm, Fluttershy's successful series of 'home care for critters' guides, and Pinkie Pie's inheritance of Sugarcube Corner when the Cakes had retired. Celestia asked questions here and there, visibly relieved when Dash reassured her that Luna had done an admirable job of managing the country in her absence, and Spark soaked up the first-pony account of life in the real world like a sponge.

Dash helped carry plates to the table and they all sat. She was surprised to see that Celestia carried two settings, and Spark took her place in front of one of them. "You can eat?"

"Oh, mine's not real food. Simulated food for a simulated pony."

"So... what's the point?"

"Sharing meals together is a very important social act, a key aspect of companionship."

Dash choked on her first bite of grass burger, her mind racing ahead. "Companionship? Are you two, uhhh..." How would that even work, come on –

Spark gave Dash a blank look; Celestia looked startled, before bursting out into peals of laughter. "Oh, Dash! I haven't laughed that hard in years, thank you, but really, don't be absurd. Of course, I mean no offense to you, Spark..." Spark turned her blank look on the princess, who sighed and nodded as if she should have expected that reaction. "Dash misinterpreted your explanation as meaning that you and I were intimately involved."

"Aren't we? We live together, take care of each other... I mean, you wrote me, for –"

"Sexually involved, Spark."

Spark ground to a halt, looking surprised. "Well, that's just silly. I'm not even capable of sexual activity! I only know what it is because I've read about it in your reference books."

It was Dash's turn to look surprised. "Wait, you can't –" She turned to Celestia. "She can't –?"

Celestia managed to look both amused and regretful. "I'm afraid not. Another piece of the simulation I hadn't completed before my accidental imprisonment. It did make for an interesting conversation the day Spark ran across the entries on reproduction in the Encyclopaedia Equestria."

Dash snorted into her hay fries. "I bet."

"And what of your... involvements, Dash?" Celestia was openly grinning now, a mischievous glint in her large eyes. "You've told me about your friends' courtships, but nothing of your own... or my original most faithful student's, for that matter."

"Well, I – uh – there hasn't really – I mean, it's not like –"

An indulgent smile. "Calm yourself, my little pony; I'm only teasing."

"Dash, why is your face so red?"

"Shut up, Spark," Dash muttered.

• • •

After lunch, they retired to one of the groups of furniture dotting the cavern. Dash stretched out on a sofa, gazing out the opening at Canterlot glinting in the distance. She frowned.

"So it's like... early afternoon, right?"

Spark's face went slightly slack as she recited tonelessly, "It is 11:12 AM, System Standard Time."

Dash blinked. Even Twilight didn't have a clock in her head. "Creepy." Spark's expression became quizzical, but Dash went on obliviously. "So, why's it still dark out? Didn't have time to make the sun shine here, either?"

Celestia laughed softly, a mellifluous sound. "Oh, I did, but within the simulation it was largely aesthetic, as the climate and so on are controlled by weather subsystems. When I was not inside the simulation, the sun would automatically raise and lower itself as scheduled, but when the system detected I was present, the automatic subroutine deactivated, allowing me to raise or lower it manually. A silly force of habit, you understand. But since going into hiding, I've had to restrain myself. The necessary spell is too easily traceable."

"What would RBD do if she found you?" Dash asked uneasily.

"I'm not entirely sure," Celestia admitted. "I assume she would attempt to kill me, and with the Black Guard behind her she could easily succeed."

"I kinda thought, yannow... actually, I'm pretty sure everypony thinks that you're immortal."

Celestia looked thoughtful for a moment before explaining, "In the real world, it would be very nearly impossible for somepony or something to end my existence, though 'immortal' is perhaps a touch too strong a word. In here, however, I'm just like anypony else, and... well, I already explained what would happen to a user who was terminated within the simulation."

"So you've hidden away all these years – centuries – because you didn't want to risk getting your mind erased?"

"Yes. A mind is a terrible thing to waste, after all, and I must admit to a certain fondness of my own." The princess grinned.

Dash blew out a breath. "But you're Princess Celestia! How in Equestria did you end up trapped inside a dinky box inside your own castle!?"

"Unfortunately, the Portal requires enormous power to stay open and active. To keep from burning out the associated circuits, it is programmed to shut down after eight hours of system time, or just under five minutes in real-world time."

"You couldn't just turn it back on?"

"As I said, it's not possible to enter commands from within the active simulation: it can only be done from outside. I never anticipated anything would prevent me from returning within the allotted time."

Dash's brow knotted. "What happened?"

Celestia looked mournful. "You happened. Or rather, RBD happened." Dash couldn't decide if she should look angry or indignant as the princess lit her horn, ghostly images beginning to coalesce between them, illustrating her words. "I don't know how much Twilight already told you –"

"Not much," said Dash, suddenly impatient to finally find out exactly what was going on. "She kept what she was working on a secret, I only found out about it when she needed a ride to Canterlot."

"I see. Well, a brief overview: for some time before my... unfortunate disappearance, I had been engaged in a project. Even immortal princesses of Equestria need a hobby, you understand, and mine happened to be the creation of what came to be a computational engine: a mechanical contrivance that was capable of carrying out very complex calculations in an instant."

Swirling mist came together to form geared mechanisms and a big complicated mass of equipment and thread; small notecards with holes cut in them appeared next to the equipment. Dash wasn't sure what to make of it.

"Some of the advanced looms used by the textile industry can store instructions on punchcards, which in turn control how the loom weaves the fibers together to produce specific patterns. I realized I could combine this idea with a mechanical calculator to produce a machine that was capable of instantly carrying out complex mathematical calculations."

The mess of gears, cotton, and cards melded together, and in a flash transformed into what might have been a very primitive version of the boxy machines Dash had seen in Celestia's hidden workshop.

"I knew such a device would result in much time saved in many different fields, but as I worked and improved my models" – the primitive machine was replaced by successively more advanced versions, and in greater numbers – "I began to realize that it was capable of far more influential accomplishments than mere number-crunching, and I eventually created the system you have entered: a simulation of the real-life Equestria." The view of the machines expanded, as though Dash was flying into them, and inside was a three-dimensional view of her home, glowing softly in the air.

Dash looked out the window again, taking in the almost-familiar skyline. "Yeah, but... what's the point? We already have an Equestria. I mean, Twilight did the same thing in her basement, making a copy of Ponyville. But even she didn't understand the point of it. She said it just... sat there."

Celestia hung her head slightly. "As I have managed to demonstrate several times, I am not all-knowing, nor do I possess future sight. Age and experience has granted me wisdom, but not infallibility. I do possess the capacity to make mistakes, and when I do, it is often with far-reaching consequences for my little ponies." The images in the air turned to confusion, angry and scared ponies running, other creatures chasing them, and Dash winced.

"Having a simulated version of the real world that ran at a much faster speed would allow me to perform trial runs, as it were: I could implement a policy change or announcement here first and let the simulation run for a time, to see if there were any unplanned side effects. With tweaking and revision and multiple runs, I could perfect all my decisions ahead of time." The view split, and showed the same image to begin with, but as the ponies within began going about their business, they all went different ways.

Dash stared at the princess. "Seriously?"

Celestia smiled softly. "Seriously."

The pegasus looked incredulous. "How is that even possible? The thing would have to know more than you, be smarter than you! How could a machine possibly predict what one pony will do, let alone all of us?"

"A large enough database of information allows it to predict the actions of ponies en masse, if not individually. I loaded it with all of equine history, all details of the entire social, political, and economic situation in Equestria and the same for the surrounding countries, a wide knowledge of psychology in all its ramifications, a wide knowledge of technology with all its possibilities, weaponry, communications, strategy and tactics, science, medicine... the entire contents of the Royal Libraries, in fact." Dash saw countless books flying into Celestia's workshop, being scanned by a glowing field.

"Every book, every scroll, every document since Equestria's founding and even earlier thanks to the Archaeology department. I can confidently and without shame state that the system does 'know more than me', more than any one pony has ever or can ever know. That's the only way it could possibly make accurate predictions."

Dash looked at Spark helplessly, but the unicorn was humming to herself and gazing thoughtfully at a game board sitting off to the side. She frowned and looked back at Celestia.

"If this thing's so smart, how come everything's gone to Tartarus? You're hiding in a cave, for crying out loud!"

Celestia nodded. "As I have mentioned, my work was incomplete at the time I became trapped. Several key aspects had yet to be built into the simulation. For example, there is no concept of aging here – that is to say, physical degradation over time." A cross-section of an earth pony appeared, vitals displayed alongside. "Every program left in the simulation now has been active since it started; they have all lived through the equivalent of a thousand years, and will go on indefinitely."

"So they don't get sick, or die of old age?"

"Precisely. A program will only derezz here through an accident, or deliberate violence." The earth pony dissolved into shards of light.

Dash thought back to the pegasus who'd clipped the pillar. He was over a thousand years old, and he died because of a stupid mistake? Then, with a start, she remembered the aerial lightpack battle. I killed programs. A bunch of thousand-year-old programs...

Another voice chimed in. You didn't have a choice, it was you or them. It's not like you killed ponies... She looked uneasily at Spark. Doesn't mean I have to like it.

"It took some time for the population to notice they weren't aging, and to realize that if left alone they would live indefinitely. Once the situation was common knowledge, it made the programs cautious; few were eager to give up immortality." The three-dimensional view of Equestria returned, this time with small glowing dots scattered across the map, which slowly began to contract to the center. "Those that still lived gathered together in Canterlot, and that is where the majority of the survivors live today."

Dash couldn't figure something out. "Okay, but where were you while all this was happening?" She was startled by an expression on Celestia's face she never imagined there: shame.

"I was here. Hiding. Exhausted by maintaining the life support spell, I was unable to prevent any of it." Spark was paying attention now, watching Celestia with a concerned look on her face.

Still utterly confused, Dash asked, "But why were you hiding in the first place? You said I – RBD did something. What happened?"

Something flared in Celestia's eyes; Dash almost took it for anger. "Corruption. During my test simulation, RBD spit her bit, as the saying goes, though 'flipped her bit' would perhaps be more accurate. Like the others, RBD was meant to represent her Element of Harmony, but it skewed away from allegiance to her friends. She became loyal to herself alone. She felt she deserved to be in charge, that nopony was a better leader than her. She brought some of the guards around to her way of thinking, and they came for me." Pain flashed in her eyes now. "I was with APP – Applejack's simulacrum – when they arrived. When she saw RBD meant to cause me harm, she forced me to leave and held them off long enough for me to escape. I – I –" Dash was shocked again to see tears running down Celestia's pained face. "I heard her screams. APP's, I mean. I of course know that she is not truly Applejack, that the real Applejack was safe and sound in the real world, but... it was little comfort."

Spark spoke up quietly. "She came to Ponyville, to the library, and found me. We ran – didn't even stop to pack anything."

Celestia sniffed, wiped her eyes with a hoof, cleared her throat. "I explained the system's true nature to Spark, and we made for the Portal, but before we could get there..."

"The Portal closed," Dash said hollowly.

"Celestia led us here to regroup, but we slowly realized there was nothing to be done. So we... settled down, built this place." Spark looked around the room fondly. "Over the years, I'd sneak back to the library to grab books, at least until RBD figured out what was going on and destroyed it."

"Spark has had to be much more careful since then about venturing outside our Smoky Mountain hideaway," Celestia said, the barest hint of admonishment in her voice.

"I'm always careful!" Spark protested. "And it's a good thing I do go out; if I hadn't, who knows what would have happened to Dash!"

"Hey! I can take care of myself!" Dash glared, but her heart wasn't really in it. "I do, uh, appreciate the help, though."

Spark sniffed. "You're welcome."

Dash turned back to Celestia. "So what now? The Portal's still open, right? Let's get going, we can finally get you back to Equestria!"

The princess hesitated before admitting, "It's not quite that simple, I'm afraid."

Dash snorted. "Seems pretty simple to me. The Portal's only open for, what, another four hours? We gotta get moving before it shuts down again." She stood, pawing at the ground.

"Celestia isn't exactly in the best condition, Dash..." Spark said reluctantly.

The pegasus eyed the alicorn. "Right... you're usually pretty tired, from maintaining the life spell?"

"It is a great drain on me, yes," Celestia said sadly. "I'm afraid there's no way I could summon the energy or focus necessary to teleport us there, and flying would take too long."

"Well, Spark can take us!" Dash whirled back to face the unicorn, grinning. "She teleported me here, she doesn't have to deal with the life spell!"

"I can only teleport someplace I've been before, or at least that I can see clearly. And even if I'd been to the Portal before, it's practically at the other end of the system, in the middle of the Badlands... long-distance teleportation with two passengers?" Spark bit her lip. "I don't know if I could manage it."

"There's gotta be another option!" Dash said, a touch of desperation creeping into her voice. "No offense, guys, but I'd really rather not be stuck inside this place forever!"

Celestia looked thoughtful and her horn glowed softly, the map of Equestria appearing in the air between them all once more. "Of course, the system includes all the major railways that exist in the real world. A branch line runs past the mountain range we're in, through Ponyville, and out to Dodge Junction, near the Badlands." A glowing line swept along the track's route. "Close enough that I believe we could manage the remainder of the trip on the wing."

"The next train will pass through our area in approximately ten minutes," Spark said. "We'd need to change trains in Ponyville..." Her eyes unfocused as she called up a mental copy of the train schedule. "I think we could make it."

Celestia turned to look out of the cavern. Dash followed her gaze, and to the right of Canterlot and farther away, she noticed a bright blue star, but it was much too low to actually be in the sky. She looked back at the princess, and saw the star reflected in her magenta eyes, which hardened in sudden determination. "Of course you're right, Dash. This may be my only chance – our only chance – to return home. We have to try." Then she looked taken aback, and turned to the unicorn sitting across from her. "Spark... my most faithful, faithful companion. You understand that if we succeed..."

Spark nodded and said simply, "It's not possible for me to leave the system." Dash winced and ruffled her wings awkwardly, and Spark noticed. "It's okay, Dash." She gave Celestia a determined look. "I belong here – literally. You belong outside, in the real Equestria. I want you to go. It's the only logical course of action; nothing else makes any sense."

Celestia looked as though she was trying very hard to not cry; her eyes shone as she spoke. "I swear to you that if... when we make it out, I will do everything in my power to correct the... the damage I have wrought here. You don't deserve to live like this... noprogram deserves to live like this."

Spark smiled softly up at her mentor. "I know you will, Celestia."

And then Celestia staggered back, as though somepony had stabbed her, almost falling to the ground. "No..." she whispered, staring madly into the distance.

Dash and Spark both rushed to her side. "Princess! What is it?!"

The alicorn raised a weak hoof, pointing out the cavern mouth. "The Portal, it's..."

Dash looked, and her belly turned to ice. Her vision shrank to a dark tunnel, centered on the bright blue star in the distance. It flashed once, twice, and then it winked out completely, leaving a pitch-black horizon and no way out of the nightmare she'd found herself in.

"Closed."

• • •

"Okay! I suspected as much, but it's good to know for certain: the last command I entered, right before Rainbow disappeared, was the one that actually caused her to disappear. It was the activation command for the device behind us – referred to here as "the Gateway" – and several of the previous commands were responsible for routing power to it and actually turning it on."

"Can you deactivate it?"

"Yes, I think so... Once I do, we should be safe – I won't enter those commands again, and it's not possible for this thing to turn itself back on. Stand over there, Luna, just in case."

Luna stepped back, watching the device closely, as Twilight entered a few commands. The faint hum that had emanated from it dwindled to nothing, and the princess turned back to Twilight and the master console, ignoring the Gateway as the light behind its gems faded to darkness.