Twilight took a few steps back from the workbench, appreciating her masterpiece. Hundreds of hours of work were plainly visible to her here, from every hastily shaped bit of metal wire to the scrawling runes around the outside. The construct hummed, its solid gold frame faintly luminous in the moonlight streaming in from outside. It was true that Star Swirl’s mirror was far finer than this—but that was his magnum opus. Twilight had weeks, and the pressure of an upset Alicorn mother breathing down her back.

“It’s kinda ugly,” Spike said, interrupting her thoughts. “Is it supposed to be so lopsided? And… how are you going to fit through there? You don’t think Flurry is just going to crawl back across, do you?”

Twilight winced, spinning slowly around. Spike stood by the door, holding a brass cage in one claw. Inside was a pigeon, trained by Celestia’s own avian experts. Right on schedule. “It’s a scale model, Spike. The first reconfigurable Worldgate ever built.”

She circled the workbench, levitating out the second half of the spell from underneath. It was a metal cabinet, filled with wires and thaumic vacuum tubes. They glowed with magic even now, warming the air around them.

“That’s reconfigurable?” Spike asked, settling the cage onto a side table. He reached into a pocket, removing a little bag of birdseed, and pouring out onto the bottom of the cage. The bird hopped down off its perch to peck at the food, chirping cheerfully at them.

“Relative to other Worldgate spells, yes.” She levitated a thick binder over to them, flipping through its contents. Thousands of diagrams were inside, most almost identical. Each one began as a circle, with jagged edges emerging as they distorted one way or another. “We have too many worlds to go through to sit around trying until something sticks. We need innovation, or we’ll be here so long Flurry will have her own foals by the time we reach her. We can’t afford to take as long as Star Swirl.”

Spike hardly even glanced at the kernel diagrams. “I’m not sure what you’re getting out of those ugly circles. Guess whoever made that book was practicing?”

Twilight Sparkle drew herself up, puffing out her chest and spreading her wings with indignance. “Spike, how could… these aren’t bad drawings of circles, these are universes.” She flipped to the front of the book, where instead of a jagged line there was a loop with peaks and valleys along a perfect sine wave. Or as perfect as Clover the Clever had managed, far into the ancient past. “This is Equestria’s world—not just this planet, but all of space and time. It’s the laws we follow, one… cosmic dice roll. All these… they’re stable configurations Clover guessed at. Some are variations he actively measured, using his ancient Amberiscope.”

“That thing you wanted from the Royal Archive!” Spike supplied, excited. “I remember that! I… don’t see any other machines in here, though.”

She nodded gravely. “Nopony seems to know where it got to. Not surprising, really. When you’re so far out from what the average pony understands, of course they don’t preserve your work seriously. Born and dead before his time. But, we have his notes! Even without the scope, there are some principles I was able to reverse-engineer. Using this log, and the mirror portal. This configuration represents my best guess at a match with the Flurry-sensing spell’s configuration.”

Spike was already tuning out. Twilight had to step it back, or she was going to lose her assistant’s attention. Once that happened, she’d be hard pressed to get him to help with this project again.

“Anyway, I’m about to open it. I’ve been gathering energy for the last few days—the spell should be ready to stay open for a few minutes.”

She was right; the instant she shifted to something more exciting—actually using the brand-new dangerous spell—he jerked right back to attention. “And that’s long enough to teleport Flurry back?”

Twilight shook her head sadly. “I wish. Teleportation isn’t so simple. A Worldgate takes a sympathetic connection. I’m Flurry’s aunt, but I still don’t know enough of the variables to fill in the rest. I don’t know where she is, or what mental or physical state she’s in. And if I try to guess at those numbers, stars only know what I’ll teleport in.” Possibly nothing, or maybe she’d only wish it was nothing. “We’re starting simple. This gate will be just big enough for our new friend there. They can fly across, find a leaf or a twig, then fly it back. Anything alive from that world will be enough to confirm I landed on a successful match with Flurry’s spell.”

“Out of all those…” Spike muttered, staring down at the notebook. Finally he realized the scope of the challenge ahead of them. “You’re going to guess it right?”

She chuckled, closing the binder with a snap and settling it back onto her shelf. “If it was a matter of guessing, it would probably take a lifetime. But we have the tracking spell on Flurry, that eliminates most of the bad leads before we waste time with them.”

Spike sighed. “Too bad she can’t just… come back the way she left. You don’t think she’s going to reverse her spell and return to Equestria?”

Twilight approached the Worldgate, flipping switch after switch in her bank. “Maybe she will, Spike. But we need to proceed as though she won’t. The worst that can happen is all my work gets wasted. If Flurry is safe, then I won’t be upset. But put your goggles on, this is gonna be bright.”

She levitated her own facemask up off the table, settling it in front of her face. She lifted a book, propping it sideways to block the birdcage’s view. No sense blinding the poor thing before its dangerous mission.

A low rumble began in the castle, shaking through its foundation all the way to the map room far above. Then there was a crack, and a flash of light brighter than the sun.

The light faded a second later, leaving a wound in space directly in the center of Twilight’s spell. The Worldgate wasn’t so much about opening their worlds as holding them open long enough to be used. Faint mist leaked out from within, heavy enough that it rolled off the bench and flowed down to their hooves. Water on the other side, that was a good sign.

“It worked,” Spike whispered, flipping up the goggles. “Buck me, Twi, you did it.”

Careful how you copy Rainbow’s profanity. But she didn’t have the heart to correct him now. Twilight felt the same excitement, just as powerful. It wouldn’t matter until after this nightmare was over, but some part of her still swelled with pride. Even without the princess thing, she was going into the history books for this. “We have about ten minutes before the thaumic capacitors deplete. Time for our new friend to take her trip. Bring the cage.”

While Spike busied himself with that, Twilight removed a little metal ring, carved with runes so tiny she couldn’t see them without a jeweler’s glass. A single shard of crystal glowed in the center, powering the enchantment.

“I have this for you,” she told the bird, levitating it in and briefly holding the animal still to secure it. “If something bad happens, it will teleport you back a few moments before the portal closes again. You won’t be trapped there.”

Fluttershy insisted that animals were as smart as ponies, in their own way. Whenever they failed to live up to this, she always claimed it wasn’t their fault. It was because they were stressed, or mistreated. But Twilight could see very little signs of intelligence in this bird now. Only terror, as it pressed as far away from the Worldgate as it could. Even without any direct magical senses, it could apparently feel that something was wrong, and had no desire to be near it. Twilight could feel a little sympathy there… but she would still send it.

“You sure about this?” Spike asked, his claws hesitating near the cage’s entrance. “It doesn’t look very happy. They said she was one of the best trained birds in the castle.”

Twilight gritted her teeth. “She doesn’t have a choice. Listen, bird. All you have to do is fly across and bring us a leaf. That’s it. Just… an opening, just like on this side. Cross, bring us a sample, and cross back. It’s all you have to do.”

To her surprise, the bird actually responded. She was probably projecting the resolve she thought she felt from her. That was what a pony might feel, as they bravely prepared for some dangerous mission. It made sense for the bird to feel something similar.

“Good luck,” Spike muttered. “Twilight knows what she’s doing with a spell. You’ll be fine.” He pulled the cage open, holding it inches from the opening in the air.

The bird took off, flying a short distance from the cage. She looked like she might be about to turn and flee—but the faint current of air pulling towards the opening was probably overwhelming from a little bird’s perspective. With one final chirp, she vanished, a single feather fluttering to the ground behind her.

“Harsh,” Spike whispered. “Fluttershy might’ve been able to convince her. We could’ve asked for her.”

Twilight shook her head. “I’m sure she could Spike, but we don’t have time to wait. Flurry doesn’t have time. It’s the easiest mission an animal could have. Just get a leaf and bring it back.”

Spike began pacing back and forth, holding the gilded cage under one claw. “What if she doesn’t come back? Maybe things are nicer over there. She’s more afraid of us than she is of whatever’s there.”

“Hence the recall bracelet. Even if she doesn’t come back on her own, the magic will bring her back when the Worldgate is about to close. If she’s not clever enough to bring a sample, maybe she’ll eat something. We can… use that.”

“Fluttershy’s not going to be happy.”

Twilight tensed, but resisted the urge to snap at him. “Then… think carefully before you tell her about this,” she said. “This is the first test of many, Spike. The chances I’ll get it on my first try are near zero. We’ll have to keep probing until we eventually find wherever Flurry has ended up.”

She glanced at the clock, expression souring. They were already halfway out of time, and there was no sign of the bird returning. You’d think if she was so afraid of this trip that she’d be rushing back as quickly as she could.

Twilight squinted at the crack in the air, probing its edges with her magical senses. She couldn’t see through to the other side, not even a hint.

“I don’t like this,” Spike said, another two minutes later. “She should be back by now. How hard can it be to find a leaf?”

“A few more minutes and she will be,” Twilight said. “Maybe you were right. We’ll have Fluttershy’s help with any other animals we recruit. I’m guessing she flew off. We’ll need to get a different bird, after this one is so upset with me.”

The Worldgate began to hiss and sputter, shaking her castle again as its internal energy overwhelmed any effort to contain it. The longer she fought to hold it open, the more power it would take. Eventually, not even an Alicorn would be able. That was why even Star Swirl’s spell stayed open for only a few days at a time.

There was a harsh crack as it failed, loud enough to make her ears flatten. No light this time—only a little sputter of sparks as the spell died.

On the plus side, the recall charm had functioned exactly as designed.

The bird wouldn’t be making it back to Canterlot, though. She’d been singed beyond belief, and smelled like she was halfway cooked into a dragon’s dinner. Twilight’s stomach turned, and she looked away from her table.

“Stars,” Spike whispered. “She’s… dead, Twilight.”

“I know.” She lowered her head, defeated. “I knew this could happen. It was… a remote possibility, but always something to worry about when you’re traveling between worlds. The place you’re connected to might not support life. From the look of her, it was… hot.”

Spike dropped the cage, fury on his face. “No more animals, Twilight. I know how much you want Flurry back, but… this isn’t right. You can’t turn into another Cadance. Figure out something else.” He stormed off, leaving Twilight alone with the corpse.