"Would you mind explaining again what it is we're actually looking for?" Professor Blueblood asked for the eighth time, flipping through another meandering tome in the archives of the Canterlot Castle library.
"The origin of the Nightmare Moon stories," Professor Heartstrings replied automatically, without glancing up from her own book. "I have some theories I need to confirm. Just because I'm stuck here instead of where the action is doesn't mean I'm going to sit by and watch helplessly."
The blond stallion frowned at nobody in particular as he smoothed some wrinkles in his suit. Once he had done quite enough of that, he put a hoof to his temple. "Is this like the time you said the little fillies' room was haunted?"
"It was!" she insisted. "I mean, it still is, no thanks to a certain Astrology professor, but that's beside the point. Look." She levitated a book she had set to the side so that he could see it. "This is a modern foals' version of the legend."
Reluctantly, he moved closer and read the story she indicated.
One day, a shadow monster came down from space and took control of the pony Princess Celestia loved most. In its new body, it called itself Nightmare Moon. The sky turned dark, and Princess Celestia fought Nightmare Moon. She couldn't hurt the monster without hurting her loved one, so she sent them both to the moon.
"That's the stupidest thing I've ever read," Blueblood stated flatly.
"Yeah, obviously they've dumbed the story down," Lyra agreed. "And... changed literally everything. That's why most foals who aren't just learning to read prefer a different version." She set the book he had read aside and held up another.
It is said that certain magics rolled over the land during the Years of Darkness like a thick, choking cloud. Some malevolent hoof took this shadow-stuff and crafted it into the perfect form of a pony. It looked, walked, and talked like a pony, but darkness and malice writhed within. It drew the evil magic into itself, and let loose magic that could rival Celestia's own. Likely its creator was its first victim, as is usually the case with such reckless experiments, but many more would follow before Celestia was able to isolate the thing.
The soap-white stallion regarded that one carefully. "Okay, that sounds more plausible. So what's so important about it?"
"About this story? Nothing at all." Lyra tapped the rest of the books she was searching through. "The important thing is that it's at least the fifth major version of the story."
"Stories change over hundreds of retellings. That doesn't seem strange to me at all."
"Well, true," she accepted, "except that the farther back I go, the more heavily restricted the book is." She gestured toward the town proper. "These two were available in the public library. Then there was the one that said Nightmare Moon was created by Discord by showing Celestia a magic mirror, that one was in the castle library. The version that said she was created by Celestia herself was in a restricted section, students need special permission to read that book. And this one," here she indicated the book she was reading at the moment, "was on that shelf over there—no students at all can see it."
It was clear that Blueblood was trying very hard to be disinterested. It had been so much more genuine when he had joined Professor Heartstrings on this errand. In the end, though, no Canterlot professor could resist the urge to ask questions; it was something they were taught early on in life, and living by it was what made them successful. "Very well," he said, succumbing, "what does it say?"
"It reads like a long, complicated mathematical equation," Lyra answered. "It's the most logical and detailed interpretation possible of the question, 'What is Nightmare Moon?' It's not helpful at all, except that it's another link in the chain."
The stallion put a hoof to his lips in an oddly dainty sign of thought. "I see. But if that's the case, why are you wasting time here? Didn't you already look through Professor Sparkle's books? I can't imagine anypony would have access to more restricted documents except for Celestia herself."
"Yes, that's the problem I'm faced with," Heartstrings agreed. "I assume that means you don't have anything for me."
"Hardly." He snorted. "This still sounds like a foal's errand, though I'm sure you'll accidentally discover something interesting in the process."
"Well, then, I should get going," she said, standing up. "Time is of the essence. I'll let you know when I've found what I'm looking for."
With that said, Lyra stepped out of the archives and into the library proper.
As the students had mostly gone home for the holiday, the library was nearly deserted. At one table an odd trio sat—two colts playing chess as the filly with them pored over Canterlot: A History. The professor paid them no mind as the main door to the library opened.
In walked a filly with a coat of burning gold, her mane the reds and yellows of an inferno. She moved with a sense of purpose—she was rarely observed to act otherwise. When she saw Professor Heartstrings, she stopped. "Professor, are you working on something?" she asked, her cyan eyes brightening.
Sunset Shimmer was a favorite student of Lyra's. She was well-known among students and teachers alike as a prodigy; even at her young age, it was sometimes whispered that she may be the next Twilight Sparkle in the making. She also had a reputation for an attitude as fiery as her blazing sun cutie mark. While her temper had gotten her into trouble on occasion, Lyra liked to think she had the filly's trust, and tried to direct that anger to better ends.
There were rumors, of course, that Sunset had some secret troubles at home, but she never spoke of them even when asked. All she ever showed was a singular drive to improve in class. And while she excelled at history, as she did with nearly every subject, she threw herself with passion into assisting the professor with her research in her other area of specialty, planar magic.
"I am," the seafoam mare confided, "but I need a little more time to gather data. Why don't you come by my office later? We can interpret my findings together."
Excitedly, Sunset nodded. "I'll be there," she promised. "Send me a note when you're ready?"
Lyra smiled. "Then I'll see you later. It'll be fun. For now, I'm going to meet with Professor Lulamoon."
~#~#~#~
"Behold! Trixie is the greatest!" Professor Lulamoon declared as the door to Celestia's office swung open. "Now, why did I do this?"
"Because I'm looking for something only Celestia is allowed to see," Lyra replied, trotting inside. "And you're the only one sneaky enough to break into her office."
"Oh. Is this like that time you said there was a mind fungus overtaking the hedge maze?" the azure mare asked.
Professor Heartstrings was, by this point, sifting through the papers on Celestia's desk. "It's completely like that, because I was right then and I'm right now. Could you check for hidden compartments, too?"
"Already on it," said the other mare, inspecting a hidden nook.
"How did you—"
"They always hide things behind paintings." Professor Lulamoon nudged the painting she had removed from the wall. "It's like Celestia didn't even want it to be a secret."
Lyra was about to join her and take a closer look when she noticed one of the desk drawers was ajar. She pulled it open, and lifted out a book. The title read "Records of the Alicorns", and it had a silver bookmark in it with the royal seal on the end.
Her mind swam with the implications of this book's existence. What lost secrets might have been kept hidden within its covers? It was only after considering the question that she realized that the tome might very well include the solution to her problem. Flipping it open to the marked page, she scanned for anything important.
Funny, it was written in Draconic. The dragons used an ancient language that Lyra was well acquainted with, and it was unlikely any other professor could have translated the words as quickly as she could.
The Starlit Princess, youngest of the alicorns, is laid in state within the tallest tower. The August Princess remains to keep vigil alone; the rest withdraw, each to her home. The Lord of the North Wind travels with them, for a shudder has gone through the planes. Something stirs at the loss of two alicorns. A great battle is coming.
"Heavy stuff," Trixie commented.
Professor Heartstrings glanced at the unicorn reading over her shoulder. "Isn't it? I think it's the clue we need, too." She shut the book. "So what did you find?"
The blue mare held up a glass bottle with her magic.
"Sweet Apple Cider. One of their more, let's say, interesting brews."
Lyra sighed. "We're going to have to have a talk with her later," she remarked wearily. "Right now, I've got to see about a tower."
As she trotted out of the office, she heard the sound of a bottle being opened behind her.
~#~#~#~
Blueblood unlocked the door to the Astrology tower. Lyra gave him a polite nod and together they ascended the stone stairs. The air grew warmer as they climbed, heat filtering down from the sun-warmed observatory chamber.
At the top, she began combing through the room's equipment. She checked the telescope, flipped through the charts and records, and felt along the walls with her magic, but found nothing.
"And you're sure the book said it was here?" Blueblood asked, leaning against the wall.
"This is the tallest tower in Canterlot, and has been since the castle was built," Lyra replied. Despite that, the astrologer's doubts seemed well-founded. There was no evidence that anything was amiss, no matter what spells she swept the room with. "You could help look too."
"I've cast every relevant divination spell that I know of." The stallion shrugged. "Not that there are many, mind you. Ancient corpses may be of archaeological value, but they're not something that most ponies tend to misplace. Really, that mostly just leaves detect secret doors, and there are none."
She stalked to the window that looked out toward Ponyville, grumbling to herself. She was close, she could feel it. Far, far below, she surveyed the lush, forested landscape…
"Gather everypony you can," Lyra said, turning and nearly sprinting down the stairs. "Meet in my office, we've got a lot to discuss. And bring a map."
~#~#~#~
The route from the library to the professor's office was by now familiar to Sunset. She trotted hurriedly down the corridor, wondering what the mare had in store. The office door was slightly ajar, and she pushed it open.
"Are you sure this isn't like the time you said that Honey Sweet was from another planet?" a voice inside asked. As she entered, Sunset could see the speaker was Professor Minuette, seated beside Professor Heartstrings at the desk.
"The filly has antennae!" Professor Heartstrings replied, gesturing wildly with her hooves. "I can't be the only one who noticed them! Look, was there a castle here or wasn't there?" She tapped a spot on the map that was spread out in front of them.
The room was looking a little crowded. Professor Blueblood was seated by the door, eyes halfway glazed over. Professor Gingersnap and Professor Inkwell were paying closer attention, while Professor Lulamoon kept trying to touch things, only stopped by the hawkish glare of Professor Arpeggio.
Minuette examined the map. "On that spot?" She consulted a book levitating beside her. "I'm not sure..." She checked over the page several times.
"No hurry, we've got all the time in the world." Professor Heartstrings sighed, rolling her eyes. Turning, she noticed Sunset's entry. "Oh, hello. Glad you could make it, and sorry we couldn't meet one-on-one today. Honestly, this has gotten a little bit out of hoof."
"What is all this?" Sunset asked. "I thought you needed my help with something."
The green mare's eyes drifted away from the filly. "Well... I do, sort of," she said. "I wish I didn't, though. See, we've kinda hit a breakthrough, but now we've got a bigger problem." Her horn lit up, and a scroll floated onto her desk. "To really make sense of everything, we need to get to Ponyville. But there's no way out. There are no chariots left, the trains aren't running, and the Gate of Magic is closed, which prevents normal magic from passing."
The scroll unfurled in front of the student. "Is this a spell?" She scanned it over. It was fragmented and confused, almost unrecognizable as anything functional.
"I don't believe it," Minuette whispered, her attention still on the book.
"It's a new application of planar magic," the professor informed her. "I call it dimension door. It would allow the caster to completely ignore both physical and magical obstacles by creating a demiplane that only consists of the origin point and destination. But I'll need your help to finish it in time. Do you think you can help?"
Sunset suddenly realized that all the professors in the room were now watching her curiously. She returned a brief glance to each of them. "I... yeah, maybe. It might take a day or two, but if the theory holds we can probably get it done before the Summer Sun Celebration is over."
"Perfect." Lyra nodded. "In that case, let's get to work."