Princess Twilight Sparkle nervously gulped as the light around her faded, revealing her location. She was in a place she had only visited once before, one year ago, just before her ascendancy to Princess-hood.

She was in Princess Celestia’s Hall of Memories.

All around her were windows into her past, showcasing the events of her life, both major and minor. Beyond was a shining void, the very fabric of the universe stretched taut. The path before her seemed to stretch into eternity, the panels and windows stretching down just as far. She wondered; what would she see if she walked just a bit farther? Would she see events that had not yet come to pass?

“Yes, you would.”

Twilight’s wonderings were silenced by the voice of her mentor. She turned and found Princess Celestia at her side, the same kind smile on her face that she always wore when in Twilight’s presence. “Did you…?”

“Read your mind?” Celestia giggled and shook her head. “You’re easier to read than one of your beloved books, my most faithful student.”

Twilight blushed and peered back at the path. “You have to admit that it’s an intriguing proposition.”

“Only the dead know the future, Twilight.” Celestia sighed and pointed her horn at one of the panels, one replaying Twilight’s first meeting with Princess Cadance. “That’s the way things must always be. To know what is yet to be would drive one to madness.” Her horn lit with magic the color of sunbeams and the window into the past suddenly became blank. “You’re probably wondering why I asked you here today.”

Twilight nodded, focusing her full attention like the student she had never stopped being.

“Today is the one year anniversary of your ascension. In that time, you have performed your duties admirably and continued to be an asset to your land and this principality.”

“Princess Luna insists it should be ‘princessipality.’”

“Princess Luna ate moon rocks for a thousand years and still insists they tasted of cheese.” Celestia rolled her eyes as the panel expanded and widened. “I have brought you here because it is time for you to learn the last great secret of your existence.”

“Last secret?” Twilight’s eyes widened. “You mean you’re finally going to tell me everything?”

“Indeed. But you must see something else first.” Celestia gave the window one final glance to ensure it was just the right size and again faced her student. “Tell me Twilight; what do you know of multiverse theory?”

“Multiverse theory is the idea that every choice we make creates a parallel universe where we made a different choice, often with huge differences than we expected. Since this theory pertains to every living creature in this universe and every single choice they’ve ever made, it stands to reason there would be an infinite number of universes, especially when you take into account that those parallel universes would also be creating their own offshoot timelines. This also ties in to what is popularly known as the Butterfly Effect, an event most popularly known from the famous short story by Braybury, ‘a Sound of Thunder.’”

Celestia slowly blinked. “I don’t know why I’m surprised.” She recovered quickly and gestured at the open window into the universe. “The multiverse is no theory, Twilight. It is very real and absolutely fascinating. I’ve spent far more hours than I’d care to reveal sitting in this hallway, looking at worlds both similar and radically different from our own.”

Twilight carefully sat. “Why are you showing me this now?”

Celestia mirrored her student’s movements. “A while ago, I set a challenge for myself. I would find what I called ‘the Darkest Timeline,’ the universe where things just went so radically wrong that it was almost hilarious.” Her horn lit and began to shape something into existence beside her.

“I imagine that led you down some pretty dark paths.”

“Oh, you have no idea. There’s the universe where your friend Pinkie Pie is a murderous psychopath. There’s another where Rainbow Dash is the cruel foremare of a truly heinous facility. I thought I’d found my goal with the universe where Equestria was invaded and conquered by misogynistic, rapist caribou.”

“…what choice created that universe?”

“I didn’t bother finding out. I managed to reach across the timelines and force their sun to go supernova.”

Twilight’s ears flattened against her head. “You murdered an entire timeline?”

“Am I not allowed to be irrational from time to time?” Celestia offered the bowl she had conjured. “Popcorn?”

Twilight nervously took a hoof-ful. “So… why am I here?”

“Because I need to show you something I accidently found while perusing the multiverse, and to do that I have to show you the Darkest Timeline.”

Twilight paused her chewing of the buttery treat. “How bad is it?”

“Pretty bad.” Celestia swallowed her mouthful. “But gut-bustingly so. Shall we?”

Still nervous and full of more reservations than she’d care to admit, Twilight nodded.

Celestia grinned, lit her horn, and touched it to the window.

The black void seemed to fluctuate and ripple like the surface of a lake or pond. Something on the other side pushed forward ever so slightly before bouncing back like rubber. An image began to form from the darkness.

Twilight braced herself for the horrors she was about to see. She stared, ready to meet the evil head-on. The image became clearer and clearer before revealing…

…the kitchen of the Apple Family’s farm house.

Twilight let out the breath she’d been holding and offered her mentor an incredulous look.

Celestia said nothing. She just shoveled more popcorn into her mouth and gestured for the purple alicorn to keep watching.

Twilight focused back on the image and watched as Applejack entered the kitchen. The earth pony looked no worse for the wear and almost seemed to glow with an inner light. She looked happier than Twilight had ever seen her. She checked something boiling on the stove, put a hoof to her mouth, and whistled shrilly. “Big Mac! Apple Bloom! Dinner’s ready!”

Twilight couldn’t suppress a smile as the youngest Apple raced into the kitchen and hugged Applejack tightly.

“Thanks, Mama.”

The smile faded. “M-mama?”

“Where’s yer pa?”

The smile returned hopefully. At least she would see what stallion Applejack had finally decided to settle down with…

“Right here.”

The smile crashed and burned into a look of horror as Big Mac entered the frame. He hugged Applejack and Apple Bloom close and pecked the orange mare on the lips.

Twilight’s eye twitched. “So… that’s not so bad. Mac and AJ are married instead of siblings and Apple Bloom’s their daughter. No big deal.”

“Oh, they’re still siblings.” Celestia grinned as Mac and Applejack’s kissing became more heated and intense, mindless of the little filly at their hooves. “They are in a deeply committed, beautiful, grossly incestual relationship whose sweaty, sinful, and deeply inappropriate sexcapades have resulted in that yellow filly right there.”

The eye twitch intensified. “But… but… children born of incest have medical defects. Sometimes mutations. Apple Bloom looks fine.”

“Look closer.”

Twilight did, trying her best to avoid watching one of her best friends desperately trying to entice her older brother to mount her on the kitchen counter. Apple Bloom was watching this happen with the happiest smile on her face… the fleshy slits on her neck flapping in glee.

“Gills. She has gills.”

“Marvelous, isn’t it? If she survives to marehood, she could lead explorations into the darkest depths of Equestria’s oceans.” She paused her munching of popcorn when she caught Twilight’s withering stare. “What? You have to look on the bright side with these sorts of things.”

“Can we please check on one of my other friends?”

“Of course. Any in particular?”

“Just so long as they aren’t birthing abominations with their siblings.”

Celestia grinned conspiratorially and again touched her horn to the window. The image rippled and faded into the interior of another familiar abode; Fluttershy’s cottage.

“This looks… normal.”

“Wait for it.”

“Wait for whaAAAAAAAAHHHHHH!” Twilight involuntarily pushed herself away from the window and screamed as the window was swarmed by a mass of small creatures. They were all equine in shape, but the rest of them…

One’s hooves ended in devastatingly sharp claws.

Another seemed to have something almost like flippers. It barked and slapped its appendages together in a horrifying approximation of what must have been joy.

Twilight felt her gorge rising at the sight of the smallest of the bunch; its multi-lobed eyes and buzzing wings identifying part of its DNA with some hideous insect.

Celestia also gaped in horror… at the sight of her empty popcorn bucket. “That’s going to go right to my flanks…” she muttered.

“WHAT IS THIS?!” Twilight finally managed to scream as she gestured wildly at the image. “WHAT IN THE NAME OF DISCORD’S UNDERPANTS AM I LOOKING AT?!”

Almost in response to Twilight’s outburst, a calming voice rang out from the window. “Alright, little ones. Settle down. It’s almost bedtime.”

Twilight looked back at the window in dawning horror. “No.”

As she watched, Fluttershy floated into view. Her mouth was alight with a remarkably satisfied smile and her newly cut short mane allowed everyone around to see it.

She was also hugely pregnant.

Twilight felt the urge to vomit returning.

Celestia, not missing a beat, stuck the empty popcorn bucket under her student’s muzzle. While Twilight bid a second hello to her breakfast, the Sun Princess conjured a glass bottle of soda and sipped it slowly. “I’d assume you’d want a seltzer water? Perhaps ginger ale?”

Twilight wiped her lips and magicked the bucket away in disgust. “What… what am I looking at?” she panted.

“Fluttershy and her children, happy as a batch of clams.” Celestia noticed something and raised an eyebrow. “Come to think of it, I think one of the little monsters might actually be part clam.”

“Why are they monsters?!” Twilight screamed. “I thought I specifically asked you…”

“…to not show you any of your friends creating abominations with their siblings. Yes. And as you can clearly tell, these adorable little beasties are not the spawn of incest.”

“Then what are they the spawn of?”

“Bestiality. Obviously.”

Twilight retched again as the creatures began to… sing to their mother. It was a ghastly, hideous noise. It was the kind of music a mother sings as a lullaby while she drowns her infants in a bathtub. It was the noise a star makes as it dies and explodes, taking whole planets with it. It was the final, gasping breath of the frog as a snake swallows it whole.

Twilight did not find it enjoyable, to say the least.

“It’s not terrible. I mean, you can’t really dance to it or anything, but I could definitely see myself humming it in the shower.”

Twilight glared at her mentor. “Please stop doing that. And please get to the point of all this. Are all of my friends sexual deviants of some kind?”

Celestia laughed and shook her head. “The dark wonders of this world go beyond simple things like that. Or haven’t you asked yourself the big question yet?”

“The big question?”

“What was the event? What could have happened that was so momentous that it caused all these horrors?”

“What…” Twilight gulped before she asked the next question. “What happened?”

Celestia barely restrained a whoop of delight as the image mercifully faded to black just as Fluttershy began nursing her hideous brood. “That’s my inquisitive student! You see, in this universe my sister was never defeated on the longest night of the thousandth year. The night ruled eternal.”

“But… but everypony would die! Without the sun, we wouldn’t get essential vitamins. The air would freeze and the crops would die! It’s not a sustainable system!”

“Quite right, something everypony realized within the next few days. And once everypony realized their days were numbered, moral constraints were thrown to the Timberwolves. Why shouldn’t Applejack and Big Mac be open about their relationship and their daughter’s true nature if Equestria has barely a year left? Why shouldn’t Fluttershy give in to her base desires and attempt to discover just how many of her beloved creatures can successfully crossbreed with a pony? Why shouldn’t Pinkie Pie discover just how delicious the taste of her fellow Equestrians can really be?”

Twilight’s ears perked up. “What was that last part?”

“Oh yes.” Celestia’s horn touched the window again, revealing Sugar Cube Corner. The cases that once held baked confections of every kind now held various chops and bits of pony, most garnished with powdered sugar and hot fudge. “You see, a large number of ponies got very depressed when told of their own imminent demises, so they volunteered themselves as food stuffs for those who wished to see things through to the bitter end. They live out their days in quiet solitude and inescapable depression until their number gets called. Then they are quite painlessly dismembered and devoured by those they once called neighbors.”

Twilight’s gaping look of horror could probably be seen from space. “But… but…”

“Oh, the butt is very much in demand. No social taboos means that you can play with your food, if you catch my drift.”

“I DON’T WANT TO CATCH YOUR DRIFT!” Twilight screamed, pulling at the flesh of her face in a desperate attempt to wake herself from this nightmare. “Ponies are herbivores! Our bodies literally cannot process meat!”

“But you aren’t meat, Twilight.” Celestia raised an eyebrow. “All ponies are made of sentient candy.”

“…what?”

“Or did you think it was normal that you all come in such a wide variety of colors?”

“But… but we bleed.”

“Have you ever tasted it?”

Twilight, far past the point of rational thinking at this point, drew a hoof across the tip of her horn. She carefully brought it to her lips and licked the wound.

“Well?” Celestia asked, the smallest smile on her face.

Twilight pulled the hoof away from her mouth and stared in wondrous terror. “Corn syrup.”

“Oh, but it gets better!” The window began to fly past scenes at a rapid pace. “Rarity takes the skins from those harvested and makes them into an incredibly popular fashion line. Rainbow Dash went mad and decided to fly up to the sun and pull it back into the sky. She’s still in orbit, frozen solid! Cadance and Shining Armor made peace with Chrysalis, started a three way relationship, and eventually reduced the Crystal Empire into nothing more than a non-stop orgy with occasional devouring of rock candy!” Celestia let out a wild laugh. “Up is down and left is right. Chaos reigns and Discord can’t enjoy it because HE’S STILL TRAPPED IN STONE!” She gestured at the window proudly. “Behold, my most faithful student, the darkest of timelines! My search is over at last!”

Twilight Sparkle said nothing.

Celestia looked down to find her student in a fetal position on the floor, rocking back and forth as she stared away from the window with purpose. “Twilight?”

“Why?”

The fragility in her almost daughter’s voice robbed Celestia of all her humor.

“Why would you show me this?”

Celestia gently stroked Twilight’s mane and touched her horn to the window one last time. “So I could show you this.”

Twilight closed her eyes and flattened her ears, terrified of what was to come…

“Dear Princess Celestia.”

The sound of her own voice made Twilight turn her head. She beheld a vision of herself as a unicorn once again, her magic scratching along parchment as she dictated a letter. “What is this?”

“It’s you.”

“But… what’s wrong with me? Am I sleeping with Gummy? Do I help Pinkie with recipes?”

“That’s just it; there’s nothing different about you. You’re exactly the same.”

Twilight watched as her other self continued writing the letter, occasionally stopping to smile at the familiar book-lined walls of Golden Oaks Library. “I don’t understand.”

“Neither did I, at first.” Celestia took a deep, steadying breath. “Forgive me, Twilight. I lost myself for a moment.”

Twilight just nodded a silent acceptance of the apology.

“After I saw this, that you were the lone light in all this darkness, I looked back at the other timelines. With only a hoof-ful of exceptions, you are there are as you are here. You are bright, intelligent, kind, and inquisitive. You are the constant, and that is your true purpose. You are the anchor for this world and all others. You are Twilight Sparkle, and your light shines across the multiverse.”

Twilight closed her eyes as he processed the information she’d just received. Finally, she looked up at her teacher and smiled. “Thank you.”

Celestia returned the smile and embraced her most faithful student. “I do believe this is the last lesson I have to teach you, Twilight. I’m sorry if it was a rough one.”

“It was… but I know why you did it. Thank you.” She lingered in the embrace, then finally pulled away. “Now, can I go home please? Before Pinkie accidently discovers that her mane is actually cotton candy?”

“Of course, but I suspect you have one last question.”

Twilight smiled uneasily. “The Darkest Timeline. You said that it came about because Nightmare Moon was never defeated.”

“Not my exact words, but go on.”

“But Applejack and Big Mac were already in a relationship at that point, so there must have been corruptions and fluctuations before then.”

“You’re on the right track.”

“So… what was the catalyst? What was the single event that rippled across time like that?”

“It’s simple, my most faithful student.”

Twilight braced herself for the huge shock she was about to receive…

“Toast.”

Twilight blinked. “Toast?”

“Toast.”

“Please… elaborate.”

Celestia giggled like a schoolfilly. “It really is a silly thing. You see, Luna and I have always shared breakfast. It’s the one meal our schedules permit us to have together. One thousand years ago, we were having breakfast and my magic faltered after a particularly strong yawn. The piece of toast I was holding fell and hit the floor… jelly side up.”

It took Twilight a moment to realize her teacher was pausing dramatically. “O-kay…?”

“Well, according to some ancient cultures, if toast landed jelly side up, it meant that there was no evil nearby. So I picked up my toast, dusted it off, and ate it. Luna later transformed into Nightmare Moon and kick-started the timeline we live in today.”

“What happened in the Darkest Timeline?”

“The toast landed jelly side down. Naturally, I panicked and sent Luna to the moon for one thousand years without a second thought, before she’d even had the chance to become Nightmare Moon. When she returned, she had been nursing a serious grudge for a millennium and had no desire to reconcile. She wasted no time in sealing me in the sun, my only respite from my prison the letters I still received from my most faithful of students.”

Twilight blinked slowly. “How much later in this timeline did Luna become Nightmare Moon?”

“About thirty seconds.”

Twilight finally ran out of bucks to give. “Thirty seconds.” She deadpanned.

“Thirty seconds, yes.”

“Thirty seconds created the Darkest Timeline in the multiverse.”

Celestia tilted her head cutely and winked. “Funny the way things work out sometimes, isn’t it?”