Lagrangian Triple Point

by MagnetBolt

Rating: everyone
Tags: Drama, My Little Pony: Friendship is Magic, Adventure, Equestria Girls, Sunset Shimmer, Twilight Sparkle, Twilight Sparkle (EqG)
Length: 10516

After high school, Twilight is thinking about what college she should go to. Sunset is more worried about what world she belongs in.

Twilight Sparkle spent most of her life alone. Where others had pictures of friends or family, she hung academic certificates and awards. She wasn't unhappy. She had everything to look forward to and a path to what really mattered in life - tenure.

Sunset Shimmer knocked her life off the rails. She didn't expect to care about anyone else. She never put 'fall in love' on her checklists. It was a surprise, but a welcome one. Hand in hand, they started on a path without knowing where it would lead.

It led here, far off in the brush, the path she'd originally walked only occasionally visible ahead, taunting her with what could have been.

An entry for the third Sunset Shipping Contest.

Thank you to all my Patreons and commissioners for supporting me!

Published 2019-08-29 17:30:02 UTC
Last updated 2019-08-29 17:30:02 UTC

Two Mares Enter, One Mare Leaves

Language is tricky. Words can be ambiguous. Meaning can be lost in the transfer from person to person. Even simply translating from one language to another is more akin to rewriting a piece from scratch and hoping the original intent shines through. Philosophers have sometimes wondered if questions of ethics and morality could be resolved simply by creating a perfect, unambiguous language where the truth could be stated as firmly as carving those words into stone.

Twilight Sparkle, holder of multiple certificates for academic excellence, owner of a whole cabinet of science fair trophies, anonymous publisher of a dozen papers in very well respected academic journals and, more recently, less respected academic journals that didn’t immediately reject her paper for using the word ‘magic’ (though one editor had tried to change it to ‘majik’), believed that math was that unambiguous language.

This is why she was so frustrated that it was fighting her tooth and nail while she tried to complete the equation she was working on.

“It’s not e, it’s not i to the pi anything, it doesn’t make any sense!” Twilight mumbled.

There was a knock on the doorframe behind her. She almost jumped in alarm, her heart skipping a beat.

“Are you okay?” Sunset Shimmer asked. “You’ve been in there all day and even you have limits to how far you can go on coffee alone--”

“I’m fine!” Twilight snapped.

Sunset held up her hands defensively. “Woah, woah! Sorry. I just wanted to know if you needed help.”

“I’m in the middle of discovering new math. It’s not the kind of thing where you can just step in and lend a hand,” Twilight said. “And you just derailed my whole train of thought! I’m so close to the answer!”

Sunset leaned on the doorframe, not quite entering Twilight’s study. “Princess Celestia told me the best way to learn is sometimes to teach. If you explained the problem to me, maybe it’ll help you think of a solution?”

Twilight twitched at the mention of Princess Celestia. “We’ve tried talking over problems and it didn’t help. Not with this or with anything else, lately.”

“Is this about Equestria?” Sunset sighed. “Of course it is… it’s just something I’m thinking of. I mean, it makes sense.”

“I know!” Twilight huffed. “No birth certificate. No real ID. You can’t coast forever. I get it, okay? That doesn’t mean I’m happy about it!”

“It’s not just that,” Sunset said, quietly.

“Let me guess, Princess Celestia sent you another letter.”

“She offered me a chance to finish my education. I’ve got a lot of time to make up for. You know, you could always take a year or two off and come to Equestria with me. If you really want to study magic, it’s the best place to do it in the world! Or… multiple worlds, I guess.”

“From everything you’ve described, it’s a peaceful, wonderful place with no internet, cell phone coverage, or cyclotrons. How am I supposed to work without the proper equipment? Whatever results I could get there I can get here. That’s how science works! The best place to do an experiment is where you can get accurate readings.”

“Come on, you’ve been there before.” Sunset smiled. “I bet if you saw the labs at the School for Gifted Unicorns you’d change your mind. We could try and make this work.”

“I don’t want to talk about it right now,” Twilight huffed. She turned back to her work. Maybe she needed more coffee. “Once I figure this last constant out I can start organizing my notes…”

Something buzzed.

“Your phone is going off,” Twilight mumbled.

“...not exactly,” Sunset said. “Um, take a look at this?”

“What? Is it another invitation from Pinkie Pie?” Twilight threw down her pencil and spun her chair around. “Sunset, I’ve seen your butt. Even if we’re talking about taking a break, we dated for a year, and if you think it’s going to make me forget that you’re trying to ditch me for-- is it glowing? Why is your butt glowing?”

“Sorry about the mess!” Princess Twilight - and even thinking about the title made the other Twilight, who wasn’t a princess, twitch just a little - said as the two stepped gingerly across crystal floors covered in bits of wire and scraps of gemstone. “I didn’t want to disturb anything now that it seems to be working again.”

“It’s okay,” Sunset said. Twilight started to fall, and a glowing force caught her, Sunset keeping her on her feet - rather, hooves - with almost unconscious ease. “Spike, don’t touch that.”

“Aww, but it smells good,” the dog-turned-dragon mumbled, putting a diamond down where he’d found it. “And I have hands now!” He held them up to show Twilight. “When we get back you’ve got to find a way to give me thumbs! This is awesome!”

“Lucky you, having hands,” Twilight grumbled, walking awkwardly with twice as many legs as she usually needed.

“So you mentioned the glowing cutie mark thing was something you’d seen before?” Sunset asked.

Princess Twilight nodded. Twilight narrowed her eyes. Was she taller than her, too? It was harder to judge heights as a quadruped, but she’d swear her copy was two inches taller. At least neither of them had anything else to compare.

“The castle is centered on an artifact we call the Cutie Map,” Princess Twilight explained. “It’s sort of like a friendship problem detector. It senses where we can do good, then it sends the appropriate ponies out to fix it. After some recent, well, incidents it hasn’t been working, but I’ve been working on a way to get it going again.”

She pushed open the doors to the throne room, and Sunset whistled at the sight. The huge crystal table in the center had been lifted several inches off its base, just enough space for a tangle of cables to fit under it, and a clear space where a pony brave enough to lie on the floor with several tons of rock hanging over their head could work on its underside.

“It’s safer than it looks,” Princess Twilight assured them. “The cables are rated to several times this load, each, and I might be immortal! Just, um, don’t go under there yourselves. It’s very delicate right now.”

“Between this and the mirror, I’m starting to think you’re really the Princess of Jury-Rigging,” Sunset said, looking around. “Are you using silver cable to route local leylines?”

Princess Twilight nodded, smiling. “Exactly! It’s a bypass for the original magical source. I wasn’t sure if it would work, because I was just trying to get a trickle across the first scrying circle to start diagnostics, but the moment I completed the circuit… well, see for yourselves.”

She flew up and motioned at the table.

“It’s a little high, isn’t it?” Twilight asked.

“Need a boost?” Sunset asked.

“Wait, I--” before Twilight could even properly protest, Sunset’s magic wrapped around her and she was hoisted into the air. Sunset joined her a moment later, levitating herself with apparent ease.

“It’s a trick Starlight taught me,” Sunset said.

“Great,” Twilight grumbled. “You could have waited for me to be ready!”

“Do you want me to put you down?” Sunset sighed.

“No, just- explain what we’re looking at,” Twilight huffed.

“Are you two okay?” Princess Twilight asked. “I’m sorry if this is a bad time. I’m just not sure what to do if you can’t…”

“It’s fine,” Sunset assured her. “Anyway, this looks like a map of Equestria.”

Princess Twilight nodded, fluttering over the center of the map. “It’s not a perfectly accurate map, especially with scale. I have a theory that the size and detail of locations is tied to the number of ponies living there, but it’s difficult to test. Regardless, this is the really critical part.”

She flew over to a part of the map far up the east coast of Equestria. Two tiny symbols were floating there, orbiting each other.

“That’s my cutie mark,” Sunset said.

“And mine,” Princess Twilight agreed. “Apparently we’re needed for a friendship mission. Isn’t it exciting? It means the map is really working again!”

“What kind of mission is it, exactly?” Sunset asked.

“I have no idea!” Princess Twilight said, excited. “It could be anything! Maybe we need to help two old friends reconnect! Or stop a war! Or a vengeful ghost might need to be put to rest!”

“A ghost?” Twilight asked.

“Well, probably not that one,” Princess Twilight admitted. “I’m not sure ghosts actually exist. But if they do and we had proof it would be even more exciting! I’ve already pulled up a train schedule and a list of things to bring with us. Spike, do you have that list?”

“Huh?” Dog Spike asked, looking around. “What list?”

“Sorry, not you, the other- Spike!”

“I’m coming!” Dragon Spike shouted, running into the room, tripping on a cable, and landing in front of the other Spike.

Dog Spike leaned down to--

“No sniffing!” Dragon Spike said, covering his tail.

“Aw…” Dog Spike sighed.

“It's okay. I remember what those instincts were like. Anyway, I’ve got the train tickets here,” Dragon Spike said, brushing himself off. “Hi, Sunset.”

Sunset waved.

“We need another ticket,” Twilight said.

“Hm?” Princess Twilight blinked in surprise. “The map only called two of us. It’s usually two of us, come to think of it.”

“Well, I’m going too,” Twilight said.

“Really?” Sunset said. “You don’t have to. I know you were working on something important…” She started to smile.

“I’m not letting you go off to the middle of nowhere without me,” Twilight said. “Besides, all it does is show butt marks, right? Maybe it really needs me, not her.”

Princess Twilight coughed. “Unless your flank was glowing, it probably didn’t--”

Sunset cut Princess Twilight off with a sharp shake of her head and a motion to be quiet.

“I mean, um, maybe you’re right. It’d be great to have you along!” Princess Twilight laughed nervously. “Spike, go get another train ticket.”

“Okay!” Spike ran off.

“...that was my Spike,” Twilight noted.

“I’ll keep him out of trouble,” Dragon Spike said, running after him. “Hey! Don’t do-- oh no. Don’t worry! I know how to put out fires! Twilight, where's the bucket of sand?”

Princess Twilight coughed. “So. Who feels like lunch?”

“Flowers.”

“There are a lot of edible flowers,” Sunset sighed.

“It was a daisy sandwich! They’re not edible!” Twilight huffed.

“Actually, I’m pretty sure even humans can eat them,” Sunset said. “It took me a while to get used to human food, so I have some experience with it. They didn’t make me sick. The apples were fine, right?”

“I guess,” Twilight admitted. She didn’t want to say they were the best apples she’d ever had, but they were.

“Are you sure you want to come with us?” Sunset asked, her voice dropping almost to a whisper. Princess Twilight was reading, but there was a tiny chance she’d hear if Sunset spoke too loudly.

“You keep trying to sell me on Horse Land, so this is your chance,” Twilight said, trying to fold her hooves several times before giving up on it.

“Well, the good thing is that we’re going to visit one of the most interesting parts of Equestria!” Princess Twilight interrupted, shoving a map and several guidebooks in front of everypony to give them something to look at that wasn’t a scowling face. “Shetland has been a semi-independent nation for almost a thousand years! For centuries we wondered just why it had been founded out in the middle of nowhere, but now we know!”

Sunset hesitated, looking at the (admittedly dated) maps. “Unless there was a fad for importing glacier ice into Equestria, I don’t get it. They’re hanging on the edge of nowhere.”

“That’s because those are the old maps, from well over a decade ago! Now compare them to these, printed just this year!” Princess Twilight dropped an atlas onto the collection of cartography, and this one had some significant changes.

“The Crystal Empire?” Twilight read, squinting through her glasses.

“Exactly!” Princess Twilight said, so excited it came out as a squeal. “When it returned, it answered geographic questions that lingered for generations! Shetland used to be an Equestrian trading outpost with the Empire, but when the Crystal Empire vanished, the trade routes dried up and they became isolated economically and culturally.”

“If the rumors are right, they’re all short, shaggy, and surly,” Sunset added.

“Well you know the joke,” Princess Twilight said. “The last time Princess Celestia was in Shetland they gave her a tray of odd pastries, and she wasn’t sure what they were, so she asked the Shettish waiter ‘Is that a scone, or a meringue?’”

Sunset giggled. “A-and the waiter-” she snorted. “-The waiter looks at it and says ‘Naw, yer quite right, that’s a scone, lass.'"

Princess Twilight and Sunset broke into peals of laughter. The other Twilight, the one who hadn’t been raised in Equestria, so lost that she couldn’t have figured it out even with the plethora of maps arrayed in front of her.

“I heard if your house is haunted, you should invite over a Shettish friend,” Sunset said. “Because when you’re not paying attention they’ll make all your spirits vanish!”

Princess Twilight guffawed. “You know what you call six weeks of rain in Shetland?” She paused, only able to hang on for a bare flicker of a moment before the punchline burst out of her. “Summer!”

Sunset fell out of her seat, still laughing. Princess Twilight caught her, and the two managed to slowly work their way down from full-on laughter to just uncontrollable giggles.

Twilight cleared her throat, and the laughter stopped like a switch had been thrown. Princess Twilight let go of her counterpart’s… whatever they were, at this point, and Sunset guiltily climbed back onto the train bench.

“I thought this was an important ‘friendship mission’,” Twilight said. “Not a vacation.”

“That doesn’t mean it can’t be fun,” Princess Twilight said. “Everything the Cutie Map has sent us out to do has been important. We don’t always understand why at first, but most missions have ended up helping whole communities that had hidden problems lurking just under the surface.”

“The map has always been right about who to send, too,” Sunset added.

“How would you know?” Twilight asked.

“Well, you know, Princess Twilight and I write to each other and keep each other updated on what’s going on in both worlds. She sends me copies of all her reports to Princess Celestia in case there’s something we can use on the other side of the mirror. I showed you those, right?”

“No, you didn’t,” Twilight muttered.

“Oh. Um…” Sunset hesitated. “Sorry. I thought I did.”

Princess Twilight squirmed in her seat and looked around for something to change the subject. An awkward silence descended over the train cabin. She started shuffling the map and papers she’d brought out, hoping she could find some detail she could lecture on. The books started orbiting around her in a way Spike would have described as ‘approaching critical mass’ until her aura abruptly shifted color, flared in a variety of interesting shapes, and winked out entirely, dropping the collection of reference books and scrolls onto the group like the most well-educated hailstorm on the planet.

“I’m sorry!” Princess Twilight gasped. “I don’t know what happened!”

“Maybe you need to practice telekinesis more,” Twilight said, smirking just a little at the joy of seeing her counterpart fail at something for once. “Let me. I’ve been practicing back home. I'm something of an expert at this point.”

Twilight focused her considerable mental energy, and her horn dramatically didn’t light up or react in any way.

“What?” Twilight tried to look up at her horn, which was exactly as easy as looking at the tip of your own nose.

The train shuddered, and even from the cabin they were able to hear the engine struggling.

“Something big is going on,” Sunset said. “Twilight, go check the engine. You can get there faster than we can.”

“What?” Twilight asked, looking around in confusion. “But I can barely even work doors!” She lowered her voice. “And why in the world would you make doorknobs when you have to operate them with your teeth?! Regular doorknobs are dirty enough!”

“I meant Princess Twilight,” Sunset groaned. “Because she has wings.”

“Oh! Right!” Princess Twilight blushed and spread her wings, jumping into the air and soaring with the grace of a particularly lavender brick all the way back down to the floor. “Uh.”

“Let me guess, no wingpower,” Sunset said. Princess Twilight nodded. “Great. So no flying and no magic. I’m starting to think your repairs to the Cutie Map weren’t as good as you thought. It should have sent earth ponies.”

“Let’s find out what’s actually happening before we start making accusations about my magical artifact repair skills. I’ll have you know after my niece shattered the Crystal Heart I made sure to learn everything there is to know about enchantment restoration.”

“And I got an A+ on the subject back when I was Celestia’s student,” Sunset countered, taking a step closer to Princess Twilight. “So maybe we should go back to the castle and I can take a look at your work.”

“You can look at my work anytime. And you’ll be shocked at how good it is.” Princess Twilight leaned in, their muzzles only an inch apart.

“Anytime, huh?” Sunset whispered. “Then how about--”

“We’re not going anywhere if the train is stuck!” Twilight snapped, interrupting them. Princess Twilight and Sunset quickly stumbled a step back from each other, blushing furiously. Twilight glared at them. “Somebody else get the door. I don’t want to kiss everyone that has ever used this train.”

“I’ve never seen an engine locked up like that,” Princess Twilight said. The three walked along the rails. Twilight had wanted to wait at the train for help, until Princess Twilight had pointed out that help wouldn’t come unless they went and got it.

“We’re just lucky it was only a few miles outside of town,” Sunset sighed. “But I’m starting to think that’s not a coincidence.”

“I doubt it is,” Princess Twilight agreed. “Something is affecting the very magical fabric of Equestria. Without my tools I can’t get exact readings on what’s doing it or why, but the area affected must be huge.”

“You mentioned an evil filly once,” Sunset ventured. “Do you think…?”

“No, it’s not the same ritual. I’d never forget that feeling.” Princess Twilight shivered. “The area of effect is very focused and instead of a gradual drain it’s just doing… something.”

She focused, and a spark appeared on the very tip of her horn, the strain clear on her face from the effort.

“My magic is still here, but I can’t make it move,” Princess Twilight said. “This is the best I can do, and it feels wrong. It almost reminds me of when I first transformed into a seapony. That first breath underwater feels like you’re drowning, but once you push past it you’re okay.”

“Is it like using magic in the human world?” Twilight asked, the first thing she’d said in almost a mile.

“Maybe?” Sunset frowned. “It does feel a little like trying to use magic as a human.”

“I wish I’d brought my magicometer,” Twilight sighed. “Or at least the oscillating antigravitometer.”

“Isn’t that the one with all the brass tubing?”

“Obviously I had to use non-ferromagnetic materials,” Twilight reminded her. “Otherwise the nuclear magnet would tear the whole thing apart.”

“Right, right. I remember the first version. That was a weird day.”

“It’s not my fault everyone’s buttons and zippers were magnetic!” Twilight protested. “Besides, once people calmed down we all laughed about it and had a toga party.”

Sunset smiled. “Yeah. It’s been a while since we had an adventure, hasn’t it?”

“Adventures are fine and all, but I’d enjoy it more if I understood what was going on,” Twilight said. She paused mid-step and looked at her hooves. “Having thumbs would be nice, too. I can’t even take notes like this!”

“At least we finally made it to town,” Sunset said. She pointed ahead of them, where the small train station emerged from the trees and low hills. “We can let ponies know the train is stranded.”

“Maybe they already know,” Princess Twilight said. “There’s a crowd waiting for us.”

“Let me guess, someone told them about a royal visit?” Twilight asked, rolling her eyes. “The last thing we need is a bunch of ponies asking for autographs.”

“They don’t look very happy to see us,” Sunset said, slowing as the crowd noticed them. They weren’t nearly as short as the jokes had implied and looked a lot more like the typical angry mob.

“Wha urr ye? Where's th' bloody train!?” Demanded the pony in front.

“Greetings, everypony!” Princess Twilight said. She cleared her throat and stepped forward. “I am Princess Twilight Sparkle, and we’re here to--”

“Bloody Princesses cannae even mak' th' trains run oan time!” The pony spat. “We need tae git this lout oot o' toun oan accoont o' she's cursed us!”

“Cursed?” Sunset asked.

“Aye! Cursed!”

“Let’s all just calm down,” Princess Twilight said. “Who’s in charge here? And why do you think somepony cursed you?”

“A'm in charge. They ca' me Peat Boggins, 'n' a'm th' mayor. Th' lassie that cursed us is this unicorn 'ere. She cam tae toun 'n' th' neist thing ye ken a' th' crops ur failing!” The pony motioned to the crowd, and a pale blue unicorn was dragged to the front, tied up with ropes and looking distinctly annoyed.

She looked at the small group and her face twisted in disgust.

“Oh great, it’s Sunny,” she muttered.

“Sunset, do you know this pony?” Princess Twilight asked.

Sunset shrugged. “She’s not really familiar.”

“Let me jog your memory,” the unicorn said. “You drugged me to make me miss my midterms!”

Princess Twilight gasped. Sunset rubbed her chin.

“Not ringing any bells. Can you be more specific?”

The unicorn grimaced. “You poisoned over a dozen ponies just to get to me!”

Sunset winced. “That does sound like me, but, um, you’re actually going to need to narrow it down a little more.” She glanced at her companions and whispered. “I was sort of a jerk back then.”

The unicorn sighed. “You forgot to carry a one in an equation in Professor Flask’s high-energy magic class and I corrected you.”

“Oh!” Sunset perked up. “I remember you now! Blue Dahlia, right?”

“Of course you only remember the parts that affected you,” Dahlia sighed. “So what, did you come here to laugh at me?”

“We came here to solve a friendship problem,” Princess Twilight said. “Which is… probably this. I mean, I’m not a betting pony but what are the odds that we’d run into one of Sunset’s former classmates, especially one whom she wronged?”

“Given any random town in Equestria?” Dahlia asked. “Pretty good odds.”

Sunset nodded reluctantly. “I wasn’t any good at friendship, Twilight, but I was an expert at making enemies.”

“No, you didn’t have any enemies,” Dahlia corrected. “You had victims.”

“Did you really poison her?” Twilight asked.

“I dumped out all the regular coffee in her dorm kitchen and replaced it with decaf,” Sunset admitted.

Twilight gasped in horror. “You did what?!”

“It was barely even a prank!” Sunset huffed.

“We were grad students! Do you know how much coffee we need?!” Dahlia hissed. “The whole dorm was in chaos! Very sleepy chaos!”

Peat rolled his eyes. “This is crakin' 'n' a', bit kin we git tae exilin’ this witch noo?“

“I told you, I didn’t do anything!” Dahlia protested. “I came out here to investigate this, I didn’t cause it!”

“We saw yer witchin’, dinnae huv a go tae gowk us!”

“It isn’t witchcraft, it’s math!” Dahlia snapped.

“Math dunnae hae letters in it!”

“Did someone say math?” Twilight asked, grinning. “Maybe I can take a look?”

“Thank you for calming things down,” Dahlia said. She pushed on her front door, and it swung open easily, the lock obviously broken. “I swear everypony in town is crazy.”

“I’m just glad we got here when we did,” Princess Twilight said.

“Looks like they tore this place apart,” Sunset said. The small cottage was covered in paper, scrolls and scrap paper layered on every surface. Books were piled haphazardly on tables and in one place had clearly been stacked to use as a seat. The only clear path went to the kitchen and back.

“No, I just hate cleaning and I wasn’t expecting ponies over,” Dahlia said.

Twilight picked up a few papers and studied them. “This math looks familiar. Were you trying to measure a shifting magical field? It resembles something I’ve been working on at home for weeks.”

Dahlia hesitated. “Are you and the Princess related? Because you two look…”

“We’re sisters!” Princess Twilight said.

“We’re not related,” Twilight said, at the same time.

Dahlia frowned. “Uh-huh. Anyway, this is where I got before they decided to blame me and throw me out of town.” She motioned to a blackboard. “I’ve been trying to triangulate the source of all this, but the local leylines are making it difficult. It’s all mapping to something, but it’s not the same as the leylines I found by dowsing.”

“You have the same hole in your equation I do,” Twilight sighed, as she read over the equation. She trotted up to the blackboard and tapped a line of numbers ending in smudges and scribbles. “It’s missing a term, but I just can’t figure out what--”

Sunset glanced over her shoulder, then grabbed a piece of chalk and added a single letter. “It’s o.”

“What? What’s o?” Twilight asked, perplexed.

“Oiler’s Number,” Princess Twilight said. “The base of the Supernatural Logarithm.”

“It pops up all the time in mathemagical equations,” Sunset said. “Everything is either zero, infinity, pi, or Oiler’s Number.”

“Celestia, I feel like an idiot,” Dahlia groaned. “Of course it’s Oiler’s. I was tracking field strength as a decay over distance. What else would I use?”

“You mean… you just had the answer like that on the tip of your tongue?!” Twilight sputtered. “But I’ve been trying to work it out for weeks! Months!”

“To be fair, most ponies wouldn’t know it,” Sunset said.

“Really?” Twilight narrowed her eyes. “So when did you learn about it?”

“Well, you know… when I was nine?” Sunset smiled sheepishly. “But I’m sort of a special case! Most students don’t learn about limits or the Supernatural Log until they’re… thirteen or fourteen.”

Twilight’s eye twitched. “Great, so all my magical studies have put me on par with a pony half a decade younger than I am!”

“Will you be quiet?” Dahlia said. “I’m trying to finish this! I just have to plug this in, multiply these together…” She grabbed a ruler and sketched a few lines. “...interesting.”

“Now that looks familiar,” Princess Twilight said.

Sunset nodded. “It’s a phase change, isn’t it?”

Princess Twilight nodded along after an extra moment. “It would explain things.”

“A phase change?” Twilight asked.

“Like liquid freezing into a solid, or boiling into gas,” Princess Twilight said. “But in this case, it’s magic itself!”

“Magical energy has a number of forms,” Sunset explained. “It circulates in the body like a liquid and is released into the environment like a gas, expanding and doing work. I mean, it’s not exactly like that, but…”

“It’s a useful enough metaphor,” Princess Twilight agreed. “It’s not actually solid, liquid, or gas, but it has some properties that are similar. The train seized up because the flow of magic through the engine went solid. We’re having problems casting spells because the energy isn’t expanding like a gas to fill the ‘shape’ of the spells we want to use.”

Twilight rubbed her temples, a headache forming that had nothing to do with magical problems and everything to do with the last few months of her life.

“Okay,” the usually human Twilight sighed. “If they’re really based on a logarithmic decay over distance it means that the field is highly localized, which fits with our experiences. The train started to struggle and you lost your grip, all over a short distance of track. Large power, small field. That should mean it’s easy to localize.”

“And I’ve been taking readings to do just that,” Dahlia said. She picked up a few binders and dropped them on the table. “It’s a little scattered because I didn’t know what I was looking for, but if we can organize them…”

“Organize?” Princess Twilight’s ears shot to attention, and she moved like a predator, sliding over to the binders. “You should have started with that!”

The other Twilight frowned and looked around. “Does anyone else hear…?”

“I love to sort and stack, all the books up on the shelf~! I can’t help but upack, all these feelings I have buried~!” Princess Twilight sang.

“No, no!” Twilight snapped. “I thought that was background music! None of that!”

“But I work better when I can sing,” Princess Twilight muttered.

“And for another thing, the last thing anyone here needs is to talk about buried feelings! Someone get me a slide rule and a compass!”

“I have to admit this was faster than a song,” Dahlia said. “Stopping it was probably for the best. Whenever the locals start singing, well…”

“Bad singing voices?” Twilight guessed.

“Oh no, most of them have wonderful vocal range. You wouldn’t know it unless they were singing or screaming at each other. The problem is that there’s a traditional fondness for the bagpipes.”

“Ah.” Twilight winced. "Wait, how do they play them without fingers?"

“It’s strange that the field is centered right outside of town and nopony noticed whatever’s causing it,” Sunset said, changing the subject and ensuring no one would ever find out how horses played the bagpipes. “If it wasn’t for these hills you’d be able to see it from town square.”

“There are a lot of local legends about the moors,” Dahlia said. “They go back centuries. Tales of shadow ponies and cults and disappearances near the full moon. The locals won’t go out there if they can help it. I came out here to investigate it at the suggestion of my thesis advisor.”

“Thesis advisor?” Twilight looked confused. “Aren’t you in high school?”

Dahlia laughed. “You’re just trying to flatter me. I’m the same age as Sunset!”

Twilight hesitated. “And... how old is that, exactly?”

“Is there any reason the locals don’t go out here?” Sunset asked. “Are we talking monsters, quicksand, or just spooky stories?”

“I believe the field has been expanding towards the town for centuries,” Dahlia said. “It grows at a geometric rate, though I haven’t determined the exact speed yet. It seems to be asynchronous and tied to cycles of the stars.”

“So even though it only recently reached the town, it might have actually been growing for centuries,” Sunset muttered. “Like the old math riddle about parasprites.”

Dahlia nodded. “If parasprites double in number every hour, and you have a barrel that can hold a hundred of them, how long does it take to fill up if you start with only one?”

“Seven hours,” Twilight said, almost instantly. “But you’d have almost no warning. At the end of the first hour you’ve only got two, and that’s barely anything. Then four. Eight. Even right before it’s full you’ve only got sixty-four in there and it seems like you’ve got plenty of room, but…”

“But you’re already out of time,” Sunset said. “This could be bad. If it’s been growing there’s no telling if it will keep growing indefinitely.”

“Going by the rates I saw in the readings, it would cover a significant part of Equestria in--” Twilight started, sketching a few numbers on the ground with a hoof.

“Don’t tell me, I don’t want to know,” Sunset groaned. “The point is we have to stop it as soon as possible.”

“Does anypony else see that?” Princess Twilight interrupted, pointing ahead of them. A dark shape stood on the rough path ahead of them. It looked like a pony standing in the shade, though with the distance and hazy mist of the moor it was difficult to tell which way they were actually facing.

“I thought the locals didn’t come out here?” Sunset asked, looking at Dahlia.

“What, are you going to accuse me of lying? They don’t!” Dahlia huffed.

“I’m not calling you a liar!” Sunset said, taking a step back. “Sorry. I’m just trying to help, and you’re the expert here.”

Dahlia scowled for a moment, but being called an expert seemed to have mollified her a bit. “It’s possible one of them came out to keep an eye on us,” she allowed. “They don’t trust me. They think I had something to do with all this.”

“It wouldn’t hurt to have a local guide,” Princess Twilight said. “If they’re out on the moors, maybe they know their way around!”

“If we haven’t bored them to death by talking about math so much,” Sunset said. “Do you want to do the introductions?”

“Good idea,” Dahlia muttered. “If Sunset does it she’ll probably try sabotaging their careers and ruining their lives.”

“Excuse me sir!” Princess Twilight chirped, as she walked up to the shadow. And walked. And walked. It was further away than she’d thought, the distance disguised by mist and the rough terrain. The form loomed over her, a ripple moving down its form. Her steps slowed.

“Twilight…” Sunset started, as the dread crept over her. “I don’t think that’s a pony from town!”

A hundred beady eyes opened, and with a mighty and echoing caw, the form exploded into dozens of crows, flying out in every direction. All four ponies dove for cover, not that any was to be found on the moor.

It was quiet again just a few seconds later when Sunset felt brave enough to open her eyes and look around.

“Okay, that wasn’t normal bird behavior,” she whispered.

“Get off me,” Dahlia huffed, her voice muffled by sod.

“Right. Sorry.” Sunset moved, letting Dahlia get up. The blue unicorn brushed herself off and managed to look annoyed that her former classmate had tried to save her life.

“What was that?” Twilight asked. Princess Twilight offered her a hoof up, which she pointedly ignored.

“Animals are pretty sensitive to changes in local magic fields,” Princess Twilight said, holding her hoof out for a few seconds longer before giving up and letting her counterpart stand on her own. “They’re probably suffering worse than we are. Maybe the tree they were perched on was a safe spot before we startled them.”

“Um…” Sunset hesitated. “What tree?”

“The one they--” Princess Twilight motioned to the empty air where dozens of crows had been perching on nothing at all. Her lavender coat turned a few shades paler. The lump in her throat refused to vanish even when she swallowed. “Maybe we should just keep moving so we’re not out here in the dark.”

“That’s the best idea I’ve heard all day,” Twilight said.

Twilight looked over the edge into the pit. Her glasses slid down her snout. She jerked in alarm and her hoof slipped an inch. The drop down into darkness loomed and Twilight panicked, throwing herself back, her glasses flying off her face. Dahlia caught her, and Twilight watched as her glasses disappeared into the shadows.

“Careful,” Dahlia cautioned. “It looks deep.”

They’d found it tucked between hills like they were a bulwark against anypony wandering into it, a pit ringed with stone, like a well built on some grand scale, so wide that a house could fall into the yawning abyss, and so deep the bottom wasn’t visible in the weak sunlight of the moor.

Twilight groaned. “Of course I’d lose my glasses. What else could go wrong?”

“Do you really want an answer to that?” Dahlia asked.

“Are you okay?” Sunset yelled, from the other side of the hole. She and Princess Twilight had found something carved into the stone and were translating it while Dahlia and Twilight had started circling around to see if there was anything else of note.

“We’re fine! Mind your own business!” Dahlia snapped.

Sunset rolled her eyes and got back to whatever argument she was having with Princess Twilight. Dahlia shook her head.

“With her around, you should count yourself lucky it’s only your glasses,” Dahlia said. “She always liked hurting other ponies.”

“She’s not… that bad,” Twilight said. She knew she should feel more of an urge to defend her, but part of her just felt empty inside, exhausted like an athlete who’d been running a marathon and only let themselves feel it at the finish line.

“Ponies don’t change. When we were in school together, she always had to be number one.” Dahlia narrowed her eyes. “I don’t know what her game is this time. She was never afraid to hurt ponies before if it meant she’d win.”

“Sunset saved me,” Twilight said. She sat down. “I don’t know what she was like before, but she doesn’t go around hurting people. Sometimes she loses her temper, but she’s… amazing.” Twilight sighed. Her shoulders felt heavy, and not just because she'd been walking with unfamiliar muscles all day.

“That’s always what the teachers said,” Dahlia muttered. “Then when their backs were turned she’d be bullying the rest of us so much that half our graduating class dropped out.”

“She’s…” Twilight hesitated.

“She’s special to you, isn’t she?” Dahlia guessed.

“We’re dating. Or were dating. It’s complicated. We’re on a break.”

“And you decided to go on an adventure together?” Dahlia asked. “No wonder you look as sour as a lemon.”

“It wasn’t my idea! Well, it was but I only came because…” She glanced at Sunset and Princess Twilight. They were laughing, probably at some kind of inside joke that Twilight wouldn’t have understood even if she’d been close enough to hear it.

“Oh,” Dahlia said. “I get it. You’re worried she’s going to replace you.”

Twilight scratched at the dirt. “I told her I wanted to go on a break because she’s been talking about moving back home. I just… sometimes it feels like I barely know her. It’s like she had this whole life that I’m not part of.”

“I think her special talent is making other ponies feel worthless,” Dahlia said. “She got kicked out of school, totally vanished for a decade, and now she’s friends with Equestria’s newest Princess.” Dahlia laughed. “And she even saved me from a mob and casually tossed me the answer to the problem I’ve been working on for weeks.”

“At least she’s not going to solve gravity.”

“Ah-hah!” Sunset yelled. With a rumble, steps folded out of the wall of the pit, a spiral staircase leading down into the depths.

“Or maybe she will.” Twilight sighed.

Twilight held her glasses up to the light. They’d survived the fall relatively well, only the right lens cracking. She tried to clean them and only managed to smear the dirt on the lenses.

“This is just like the ruins under Hollow Shades,” Princess Twilight said. “It must have been built by the same group.”

“Does that you know how to turn on the lights?” Sunset asked. The bottom of the well was just barely lit by the distant sky, but even with their eyes adjusted to the gloom, they could only make out a forest of stone columns around them.

“Yes! Well, actually, no.” Princess Twilight sighed. “Not without magic.”

“Good luck with that,” Dahlia said. “I can’t even make a spark to light a torch.”

Sunset rubbed her chin. “There is one thing we could try.”

“Is it going back to town and borrowing a lantern?” Twilight asked.

“Nope!” Sunset grinned.

“Of course not,” Twilight mumbled, settling her glasses on her nose and making peace with the fact she was going to be half-blind. “That would be too easy and you couldn’t show off.”

“So this is a little theoretical, but there’s a technique for pumping so much energy into magic that you can force a phase change, in the opposite direction from the freezing effect we're getting in this field,” Sunset said. “It’s like turning gas into plasma.”

Princess Twilight nodded. “It’s not every practical, though. You can’t use high-energy magic in any spells. It couples with itself in unpredictable ways.”

“Right! But if the local weirdness is forcing everything down an energy level, maybe we can still manage some simple spells.”

“It’d be like trying to write your name by pouring ink out of an inkwell onto paper but…” Princess Twilight tapped her chin in thought. “Okay. Everypony stand back. If something goes wrong, it could thermalize.”

“You mean it could explode,” Dahlia corrected. She grabbed Twilight’s hoof and dragged her behind one of the stone pillars.

Princess Twilight braced herself, legs spread shoulder-width apart. A pressure filled the room, like the feeling before a storm. Sparks raced around the spiral of her horn. Light burst like a flashbulb with blinding intensity before fading to nothing.

“It didn’t work?” Sunset asked with obvious disappointment.

“Hold on, I think I got it,” Princess Twilight said. “Look!”

A ball of fuzzy, dim light floated in front of her horn, growing brighter by the moment. Twilight tried to look, and Dahlia pushed her back into cover until it was clear nothing was going to explode unexpectedly.

“It’s definitely not an efficient way to do this,” Princess Twilight said. “But I guess we don’t have other options.”

“How dangerous is it?” Twilight asked.

“Not at all,” Princess Twilight assured her. “It feels like trying to fill up a balloon with a hole in it. If I lose control it’s just going to deflate, not pop.”

“The light reminds me of a low-pressure sodium lamp,” Twilight said. “At least we can see now.”

“Look at this!” Dahlia gasped. She’d walked in the other direction, and hidden in the shadows just outside the circle of dim light provided by the skylight of the well was a door, built to the same massive scale as the hole itself. Every inch of it was carved in a mural stretching from floor to ceiling.

“It looks like… ponies?” Twilight guessed, squinting through her glasses. She leaned in closer to try and get a better look. “Is it mythology or history?”

“Equestria’s written history is spotty,” Sunset said. “A lot of places go for decades or centuries without contact by the outside, and there’s almost no long-distance communication compared to the human world. It’s really hard for ideas to spread, so things get forgotten, like whatever this place was.”

“I recognize some of the carvings,” Princess Twilight said. She moved the wobbling ball of light over to the wall. “Look. I’m sure this is Star Swirl!”

“Hold on,” Sunset said. A blinding wash of light splashed over the wall as she created her own lamp. “Okay, that’s better,” she said. “If that’s Star Swirl, this must be Clover the Clever.” She pointed to a tall, lanky pony next to him. “They’ve got the cloak.”

“That means this part depicts the period after the founding of Equestria when Clover left to study every type of magic in the world,” Princess Twilight said. “And next to it is Star Swirl’s disappearance, then Discord’s rule…”

“It must be a historical record,” Sunset said. “But… wait, this depicts the return of Nightmare Moon. That’s impossible!”

“Is she someone important?” Twilight asked.

“Ask Vice-Principal Luna,” Sunset snorted.

“Nightmare Moon was a…” Princess Twilight tapped her chin. “Well, I suspect she was sort of a parasite or alternate personality or possibly a curse. It’s a difficult subject to talk about with Princess Luna.”

“Nightmare Moon was Luna, consumed with jealousy and trying to destroy everything,” Dahlia said. “It’s not hard to understand. Some ponies just have a bad streak, like Sunset.”

Sunset rolled her eyes, trying not to snap at Dahlia and prove her right.

“Why is it impossible for it to be here?” Twilight asked, changing the subject.

“Because she only came back a few years ago,” Princess Twilight explained. “My friends and I defeated her. This door is at least a few hundred years old, and with the way it’s buried underground and protected against the elements it could be a thousand years older than that and we’d never know it!”

“Let’s just get it open,” Sunset suggested. “I bet whatever’s we’re looking for is inside.”

“We can agree on that,” Dahlia nodded. “You don’t build a creepy underground temple in the middle of nowhere just for fun.”

“First we should check for traps,” Princess Twilight cautioned. “Daring Do says anything valuable enough to put in a vault that hasn’t been stolen after a few centuries has something guarding it, and if nopony is around that means traps.”

“I know you’ve got a reputation as the Princess of Books, but Daring Do is a fictional character,” Dahlia retorted.

Princess Twilight rolled her eyes. “Yes, I often have tea with fictional characters.”

“Really? You do that too?” Twilight asked, surprised. “Because there’s this roleplaying game I play called Otome Art Teatime and one of the capture events is making and brewing tea in realtime and if you try to fast forward through the event the capture target yells at you for not taking it seriously… you were being sarcastic.”

Nopony looked at each other for a long, awkward moment.

“I feel like I’m missing a lot of context on what any of that is,” Dahlia said. “Is this some kind of bedroom thing?”

“So as a sudden change of subject, does anypony know how to open a giant stone door without magic?” Sunset asked. “You’d think with all the adventures I’ve been on I’d learn to start taking a crowbar with me.”

“Let’s all try opening one side,” Princess Twilight said. “There aren’t real handles, but we can get a grip on the carvings.”

“Let’s all try the same side,” Dahlia said. “On three?”

The four ponies grabbed at what they could, hooves clutching stone feathers, legs, and in Twilight’s case a place that would have been very inappropriate if it had been a living pony.

“Three!” Dahlia yelled.

The door scraped and scratched as they pulled. For something unknowably old and buried underground it was in good condition, which was a blessing since even with the hinges working smoothly and the frame in perfect alignment they were still tugging on several tons of stone without a proper grip.

“Just a little more…” Dahlia grunted, throwing her whole weight into it. The door scraped and shuddered, jumping with a crack of breaking rock and falling dust as it broke through whatever it had been caught on.

A shaft of purple-green light radiated out of the crack, and the room filled with the static and ozone that Twilight was familiar with from her own experiments. It was the kind of feeling that made her wish for safety goggles and a lead apron.

“Oh wow,” Dahlia gasped, peering through the narrow gap they’d opened.

“What’s inside?” Princess Twilight asked.

Dahlia didn’t answer, just staring.

“That’s a good sign,” Sunset said. “Slam it closed or open it up more?”

“Open it more,” Princess Twilight said. “We already know burying it isn’t going to solve the problem.”

Working together, the three managed to lever it a little further to see beyond. The next room was filled with light and energy, all focused on a spinning tangle of metal and crystal, the array humming with power and half-sunk into a pool that was softly illuminated from below.

“If there’s anything I learned from my third-grade science fair, it’s to be worried about anything producing that much Cherenkov radiation,” Twilight said.

“This explains everything,” Princess Twilight whispered. “It’s a transverse orrey! Like astronomy crossed with divination! They were using this place to divine future events without influencing them!”

“I thought those were only theoretical,” Sunset said.

“Everything is theoretical until you build it,” Princess Twilight said. “I just didn’t think anypony had ever done it. You need a ton - a literal ton, because it’s a counterweight - of solid magic to keep it balanced in the W-axis. The kind of engineering and cost you’d need to do it would bankrupt a country, and if it started to decay…”

“Let me guess,” Twilight said. “If it started to decay you’d get exactly the kind of effects they’ve had here for centuries. It’s not just a weird magic blip, this whole thing is fallout from a magical reactor failure!”

Princess Twilight nodded. “It’s strange, though. All this stone should have shielded the outside.”

“Is it even safe to be this close?” Twilight asked.

“It should be fine for now,” Princess Twilight said. She motioned for Twilight to come closer and pointed at the base of the spinning orrey. The glowing water was running from one wall and out the other. “Water is a natural magic insulator. Most of the thaumatic radiation is going into it and being carried away.”

“The water table,” Dahlia gasped, snapping out of her daze. “That’s it! It’s why the field wasn’t mapping strongly to the leylines! The decaying counterweight is being eroded and the contamination is in the ground water!”

“So much for seeing the future,” Sunset said. “They didn’t even see far enough ahead to avoid getting other ponies hurt when they built this.”

“In theory, since the transverse orrery doesn’t actually affect the timeline it’s possible once it was built they were unable to actually avoid this outcome,” Princess Twilight said.

“So time travel is a predestination paradox?” Twilight asked. “You can’t change the future?”

“Oh you definitely can,” Princess Twilight said. “It just takes a lot more effort and an absurdly powerful unicorn with a grudge, several magical artifacts, and no sense of appropriate response.”

Sunset paused. “Starlight Glimmer?”

“Right, you two have met.” Princess Twilight took a deep breath. “Anyway, ideas?”

Sunset looked around. “Close the drain and let the room flood?”

“That would be the safe thing,” Princess Twilight agreed. “I’d really like to take some time to study the carvings…”

“You can come back later with reference materials,” Sunset said. “And it’ll be a lot easier to get them down here if you can use magic.”

“You’re right,” Princess Twilight agreed. “We’ll need cameras, rubbing paper, charcoal, sample containers with proper labels, crates to sort it all in… oh I can just picture it now! We’ll need to come up with a reference system that takes note of the position on the wall, the height above the ground, surrounding carvings…”

“One thing at a time, Princess,” Sunset giggled.

Twilight cleared her throat, and Sunset’s giggle died.

“And how do we close the drain?” the lavender unicorn shaped human asked.

“The good thing is, whoever built this place left controls out in the open instead of making us solve a puzzle to ‘prove ourselves worthy’ of pulling a lever,” Dahlia said. She stepped up onto a platform raised a step above the rest of the floor. Levers made of the same mix of metals as the orrery waited to be pulled. “Clearly this place was built by scholars instead of whatever crazy ponies build temples in those Daring Do books.”

“Scholars would have labeled them,” Twilight said. "No, actually, engineers would have labeled them. Scholars probably would have forgotten and then left it to grad students to label later."

“There are some pictograms,” Dahlia said. “Bring the light over here.”

Princess Twilight stepped closer, looking over Dahlia's shoulder. "That's odd. I don't recognize the language."

"Maybe it's not a language," Twilight suggested. "I read a study once about ideas on sending messages to the far future, thousands or even tens of thousands of years. The researchers knew no language would survive long enough, and it was entirely likely any history or knowledge of the location and artifacts would be lost. If you had to contain something deadly for that long, you'd have to use pictures and universal symbolism."

"But they'd know who would be reading it, right?" Dahlia asked. "So if we just pick one, they should have made it the right lever to pull. We just have to be confident."

Dahlia picked a lever and yanked it down. The floor shuddered, and hidden gates and clockwork moved behind the walls.

“Did it work?” Dahlia asked. The flow of water across the orrey’s base slowed to a trickle and stopped. Twilight felt her mane start to stand on end. The glow changed color, and the stone under her hooves began to vibrate.

"I think things just got worse," Sunset whispered.

The orrery started to move, sparks pouring from overextended joints as the exposed counterweight started moving in directions and dimensions that it was not designed to support. Welded joints cracked and a bolt of lightning cracked out of the machine and into the stone, annihilating a carving that would have finally explained the mystery of Commander Hurricane's gender.

A second bolt hit the ground, tiles exploding into ceramic shrapnel.

"Take cover!" Princess Twilight yelled. "It's going critical!"

Dahlia saw her life flash before her eyes. Literally. The shattering, twisting eye of the machine came to rest on her and for a moment she saw her whole life from beginning to now. It would have been educational if not for the beam of death trailing right behind the revelation.

Everything went white.

Dahlia opened her eyes cautiously because she wasn’t dead yet and didn’t understand why.

Sunset stood over her, the crackling beam of magic hitting her horn like a lightning rod. The impact almost knocked her over, sparks grounding through her hooves. She slowly turned her head, gritting her teeth. The edges of her mane and tail steamed and smoked like matches.

“Sunset!” Princess Twilight screamed, running for her. A second pulse hit Sunset’s horn, and the shock threw Princess Twilight back.

“Everypony stay back!” Sunset yelled. “I have to… ground it!”

Crimson magic wrapped around her horn, and the sparks trailing down her body were pushed back, warring forces focused to a point at the very tip of her spire before she tossed her head, redirecting the wild magic into the wall.

The carved stone exploded, and water rushed inside, knocking the orrery off-kilter and rapidly refilling the basin under it to overflowing.

Sunset collapsed, water rushing over her and extinguishing her charred mane.

Princess Twilight galloped over, trying to help her up, holding her head above the rising water.

“She saved me?” Dahlia whispered. “But…”

“I told you. She’s not the same pony she used to be.” Princess Twilight said, quietly.

“Is she…?” Twilight asked. She was barely able to say anything. Her heart was in her throat and the words came out strangled around it.

“She’s got a headache like Diamond Dogs decided to mine her skull for gems,” Sunset groaned. “Does anypony else smell burning hair?”

“You might need a manecut,” Princess Twilight sighed, her wings slumping as she relaxed.

“I’ve been thinking of changing up my style anyway,” Sunset joked.

“Sunset?” Dahlia said. “I’m sorry. I’ve been--”

Sunset held up a hoof. “It’s okay. I was pretty awful to you when we were in school together. Probably. I barely remember any of it. And that’s part of the problem! I hurt other ponies and it wasn’t even important enough for me to think about it.”

“And you’re not like that anymore,” Princess Twilight said.

Sunset shook her head. “I still fall back on bad habits, but I have friends. Friends who remind me when I’m slipping, and who I care enough about to feel bad about hurting them.”

She looked at Twilight.

“At least, that’s what I thought.”

“Let’s get back to town,” Twilight said, quietly. “We’ve stopped the problem, right?”

“The rubble from that wall Sunset blew up blocked the drain,” Dahlia said. “It shouldn’t contaminate the groundwater anymore. It’ll still take weeks for everything to go back to normal.”

“Sounds like you’ll be able to write a good thesis paper about all this,” Sunset said. She struggled to her hooves with Princess Twilight’s help. “This is your discovery. You were the first pony to see the orrery, you did all the hoofwork tracking it down, so you should start thinking of what you’re going to name it.”

“Maybe you can help me with that,” Dahlia offered. “If it wasn’t for all of you coming here to help, I’d be kicked out of town by now.”

“How about an anonymous contributor?” Sunset asked. “But in return I want a copy of the finished paper with everything you discover down here.”

“Deal!” Dahlia giggled.

Sunset shivered and looked at her butt. Her cutie mark was glowing and pulsing.

“What does that mean?” Sunset asked.

Princess Twilight turned so Sunset could see the matching booty call. “It means we solved a friendship problem. And probably saved all of Equestria. You’d be surprised how often it’s the same thing.”

Twilight glanced back at her own butt and frowned.

“Do you think she’ll be okay?” Sunset asked.

“Definitely,” Princess Twilight said. “She defeated something that’s been hanging over her for a decade and a half.”

“Yeah, me,” Sunset snorted.

“Her fear of you, and that she wasn’t adequate,” Princess Twilight corrected. “I used to have panic attacks every day because I was worried I wasn’t measuring up, and I didn’t have you to compete with. For her, it must have been like facing an impossible wall.”

“I can’t imagine,” Twilight muttered, watching the taller, immortal, more successful version of herself smiling happily with her… she wan’t sure what they were to each other.

“There are probably a lot of ponies like her,” Sunset said. “Ponies that I wronged and suffered because of it.”

“You know, not that long ago I tracked down the ponies I went to school with so I could reconnect with them,” Princess Twilight said.

“How’d that turn out?” Sunset asked.

“I was terrified! I thought I was the worst friend ever because I just ditched them to move to Ponyville.” Princess Twilight sighed, but smiled. “It was hard work fixing everything, and really hard confronting the pony I used to be, but it was all worth it in the end.”

“Maybe I should do something like that,” Sunset said. “Find all the ponies I hurt…”

“I can get the yearbooks from the School for Gifted Unicorns and we can make a list!” Princess Twilight said, excited. “Trust me, you’ll feel a lot more welcome once you’re not worried about running into an awkward situation.”

“I want to go home,” Twilight blurted out.

Sunset blinked and looked over at her.

“I don’t belong here,” Twilight said. “I hate the food, I barely understand what people are talking about, all the pronouns end in pony like that’s not subtly racist, and I don’t even have thumbs! I just want to go back to my apartment and my life.”

“I… yeah,” Sunset sighed. “We’ll head back when the train gets back to Ponyville.”

“Not we. Me.” Twilight took off her glasses so she could look at Sunset without a layer of grime and scratches between them. “I can’t be a part of your life right now. Not like how we were. This is where you need to be. My booty mark didn’t even glow like yours. You were right that I should have stayed at the castle. I shouldn’t have even come to Equestria.”

“But--”

“You’re going to object because you don’t want to hurt me,” Twilight huffed. She rubbed her eyes. They were blurry, but it was just because she couldn’t see well without her glasses. “You know what hurts? Not knowing anything about you. You had a whole life here that I don’t know anything about, and my research is just child’s play to you.”

“Sorry,” Sunset mumbled.

“Maybe someday…” Twilight hesitated. “It feels like you were humoring me. I still want to be your friend, but I need to be the friend of the real you. The one who knows everything about magic and goes on adventures and is apparently in grad school.”

“And is a pony,” Sunset said.

“You’re a cute pony. I’m okay with that part.” Twilight smiled, but it hurt. “When you make that list of people you need to apologize to, put me on it. Near the bottom. I’m going to need some time.”

“Is it okay if we still hang out?” Sunset asked.

Twilight opened her hooves and pulled her into a hug. “You better. I want us to be best friends again someday. I’ll even visit you here in ponyland if you promise not to hide things.”

Sunset nodded and sniffled, trying not to make a snotty mess.

“I’m keeping the oscilloscope though,” Twilight mumbled. “You can have the spectrograph.”

“The one that broke after you tried to find the emission lines of orichalcum?”

“It might need some minor repairs. Just like your hair.” Twilight and Sunset pulled away from each other.

Sunset touched her mane, the edges burned to black where the magic had scorched it. “I guess I will need a trim. Maybe you could help me pick something out at the spa before you go?”

“Yeah,” Twilight smiled. “What are friends for?”

Blue Dahlia rubbed charcoal over the faint etching in the rock. Now that she could get magical lanterns in the room, things were going much more quickly.

“Let’s see…” she muttered. “This seems to show the orrery itself being destroyed. I guess they really did see the future.”

Dahlia held it up to the light, comparing the carving to the room. She blinked, and lowered it, then raised it again.

“Woah…”

It was practically a mirror image, the perspective on the rock from exactly the place she was standing. Dahlia could even make out the scaffolding she’d set up on the far wall.

“That’s freaky.” She grabbed the camera and took a picture, trying to capture the right angle. At the back of the room, something glittered with the flash. Dahlia held the camera up high to keep it from getting wet and splashed through the fetlock-deep water to the far side of the orrery’s wreckage.

The flood had shifted silt and dust away from a carving near floor level. Gems had been set into it, giving it a splash of color the others lacked.

“Huh,” Dahlia said. “That's Princess Twilight, and that almost looks like Sunset, but the mane is all wrong.” She brushed dirt away from the engraved lines. “Not that it’s the only thing they got wrong. So much for seeing the future. I bet Sunset will get a real kick out of this...”

She smiled and snapped a photo of the two alicorns.