It was too loud to have much of a conversation in here. Twilight still felt drained, but not so exhausted that she would just let the insanity she'd just witnessed slip by. One of her best friends had just killed a pony before her eyes, except moments later he had risen to his hooves and spoken to Twilight as though nothing happened. She herself had teleported a pony who should've died traveling at the speed of an express train, to who knew what fate when she hit the ground.
So despite the noise, despite her momentary weariness, Twilight spoke. "What in Celestia's name was that?" she asked. "None of that... I guess I don't know what's possible any more. Thank Celestia I didn't bring Spike with me..."
Their swords would've done little to a dragon's sturdy scales, but that didn't mean he was invulnerable.
Rarity nodded, casually undoing the little ribbons that bound her mane. "That is fortunate. I've known dragons to get into this business, but Spike... he simply lacks the temperament. It would destroy him. It would destroy most ponies, I'm afraid." Her eyes narrowed as she looked Twilight over. "It's best if you just forget any of this happened. We should be passing through a few little towns on our way up to Canterlot. We can find you an opportune place to jump. You said something about a long-range teleport..."
Twilight wanted to scream. Her friend had no idea what she'd seen and done. She had gone beyond death, walked the Underworld—did she really think Twilight couldn't handle herself? I wasn't exactly Daring Do back there. But she banished that thought too. "Rarity, I'm not leaving without an explanation. I'm a princess now, do you really think I won't be able to find out what's going on here? A few messages in Canterlot... either I'll find out exactly what this is, or I'll blunder into those ponies who attacked you without you there. I think I deserve an explanation."
Rarity sighed, removing a crank from her case and beginning the difficult job of reloading her crossbow. It took an enormous amount of force, but she had her magic and few ponies had as much simple concentration as Rarity. Twilight had seen her sew whole wardrobes all at the same time. "I suppose... there's nothing for it, Twilight."
She advanced, eyes narrowing to slits. "But I must have your word this information does not reach the others. Normally when you discover something like this you gather up everypony, maybe warm up for a song, and try to work out everything in a few minutes. You must give me your solemn oath to speak nothing of this."
Twilight lifted her horn, and a little bubble of force appeared around them. The sound of the engine, the grinding on the tracks, it all vanished. Her brother's shielding spell could do far more than sound, but there was no rule that said Twilight could only use powerful spells for what they'd been designed. "There. Nopony will hear us."
Rarity deliberated for a few seconds more, before finally nodding in submission. "You're more aware than most that Equestria is dangerous, Twilight. We've discovered creatures that many other ponies believed only existed in myths. We've traveled to exotic locales, met with movers and shakers, that kind of thing." At Twilight's nod, she continued. "Do you really think Equestria could've survived this long with only the six of us to solve difficult problems? That every time some incredible villain arose the entire nation would've been at their mercy?"
She didn't give Twilight a chance to answer. "Obviously not. Princess Celestia has been aware of these dangers for some time. Many thousands of years, in fact. Long ago, an ancient order called The Knights of the Pillars was established, to protect Equestria from threats that ponies were better off not knowing about. You know how ponies are like... just look at Ponyville whenever something unusual happens. A zebra moves into the forest nearby and there's practically a riot. But obviously somepony has to fight back. That's us... the order is still around. I've been fighting monsters since I was very young. Trained, since..." She lowered her voice, but in the sudden silence Twilight could hear her fine.
"Since the attack that killed my parents."
Twilight gaped. "Your parents aren't dead. I've seen them visiting a few times. They... do like their vacations, but..."
Rarity pointed through the bubble at the engineer. "See that pony out there? He's a thrall. No will of his own... can't do anything except what he's been told. And he'll obey with exactness. He’ll drive this train right off a bridge and not have a second thought about it. There's no reversing the spell, no curing him... his mind has been completely destroyed. The soul is gone, but the body lives on. Created by... vampires."
Twilight Sparkle might've laughed at that word, were it not for her last two days. Now, though, she knew better than to assume anything that sounded strange could only be fictional. With that one word, so much of what they'd seen tonight made sense. The fangs, a warrior apparently killed but rising again once the stake was pulled free. Rarity's willingness to fight these beings with such disregard for the harm she caused.
"They're real," Rarity said. "Or at least, they have been for a long time. One of the legacies of Nightmare Moon's... well, it doesn't matter. Celestia banished her long ago, and we defeated her more recently, but that didn't undo all her work. Some of them date all the way back to the rebellion, her most trusted generals, sorcerers, and advisers. They don't age, don't grow weak... but they do feed on ponies. Take too much, and you get a thrall. Stop before that..." Her voice kept getting lower. The crossbow slumped in her magical grip. "Because somepony walked in on them before they could finish feeding... somepony with a cart of magical gems and a helping of good luck... and you get my sister."
Twilight winced. Of all the things Rarity could've said, that might be the most confusing. "I thought... Rarity, I just saw your sister, she's fine. I've seen her walking to class, I've seen her out playing with the Crusaders. She’s not a... she's not a vampire."
Rarity no longer seemed like she was on the edge of tears. "If you're thinking of the sun, that weakness only applies when they haven't eaten in a long time. So long as they get blood, they can pass for one of us. And the longer things go, the worse it gets. Check Sweetie Belle's attendance record next you get the chance. Her teacher thinks she has a rare blood condition, and... well, I suppose she does."
That thought just got darker the more Twilight considered it. If her sister was a vampire, did that mean she wouldn't ever age? She'd never get her cutie mark... all her searching was vain.
"After I killed that... thing... the Knights found me. Recruited me. And I've been hunting ever since."
"Hunting vampires?" Twilight asked. The words felt strange on her tongue, impossible to believe. But after everything else she was believing now...
"Hunting a cure," Rarity corrected. "But yes, quite a few vampires. It's possible to keep a vampire alive without anypony getting hurt. Enough donor blood, and the hunger won't drive them crazy. Equestria is a... properly civilized place. Most of them are registered. They have their donors, their supervisors to check on them. If you're alright with being the first pony the guard ever calls on when someone goes missing... you can live an almost normal life. But I plan on giving Sweetie Belle more than that. The thought of her, trapped so young, long after I'm gone. If she doesn't have enough understanding friends, or makes a mistake..."
Rarity straightened. "Most of Equestria's monsters are known. We aren't searching for them, we're searching for the ones who go bad. I sometimes have nightmares... of my sister..."
Twilight Sparkle leaned forward, embracing her. "It's okay, Rarity. I'm sure there's a way. All the other insane things I've seen lately, I can't imagine there wouldn't be. Maybe Starswirl got around to that."
“Oh, there is.” Rarity didn’t break away from her. “That’s what tonight is all about. I’m going to steal it.”
Twilight felt the chill of cold wrap around her chest as she remembered the words of the Underworld boatman. All this time she’d spent tracking Rarity and sticking a hoof in her plans, all for this moment. This had to be what she wasn’t supposed to do.
“From… the most powerful vampire in Equestria,” Rarity went on, sounding a little faint. Almost like she realized the insanity of what she was suggesting. “Out of the best-protected vaults bits have ever constructed.”
Twilight’s eyebrows went up. “If there’s a cure, why would a vampire want to hoard it? Doesn’t… fewer vampires mean fewer rivals for blood?”
Rarity shook her head. “If the Crown could locate the cure, we wouldn’t just give it to the ponies who were interested. We’d give it to all of them, whether they wanted it or not. It’s actually right in the Knight’s motto. ‘We will purify those twisted by the night.’ And as it turns out, the ancient and powerful vampires like what they have. They aren’t trapped as foals, and the idea of growing old doesn’t interest them much.”
“But you know about it,” Twilight went on. Could she get Rarity to see the flaws in this plan before the unicorn got herself killed? There was a kind of teaching that could take her through the facts slowly and inoffensively enough that she should be able to make the connections on her own. “Even though you work for the other side.”
They were traveling up a set of steep switchbacks now—the final leg of the train-ride before Canterlot itself. If Twilight was going to convince Rarity to change her mind, she needed to do it soon. “It’s a… complicated, indirect chain of informants and evidence,” Rarity said. “Explaining it all would take half the night. But yes, I’m certain. It’s possible he doesn’t even know what he’s holding. It’s an artifact… an ancient, powerful object, predating Equestria. Somehow it is the key to creating a cure.”
“And Celestia knows about this?”
“It would be Princess Luna,” Rarity corrected, casually. “She’s the one who oversees the, uh… children of the night. But no. There are informants on both sides! Even if a meeting with her was secret—word of my mission would spread before I could arrive. If the princess had given me permission, the cure might be moved or destroyed before I could reach it. It had to be something of my own initiative.”
Twilight’s eyes widened. “Y-you mean we’re… b-breaking the law?”
Rarity rolled her eyes. “Look back in the train behind you, Twilight. We’re fighting creatures that do more than lie and steal. That stallion is worse than dead. My parents are like him. Oh, it’s always a rogue element, caught and punished! There are so many justly punished criminals trapped in Tartarus and the dungeons of Equestria. But what good does punishment do for them? My parents don’t care that I got revenge. If they could tell me anything—they would want Sweetie to have a normal life. How many other cases like hers do you think there are?”
I’m in over my head, Twilight realized. It was more or less what Rarity had told her when she arrived here, and now she felt it powerfully. This was an ongoing cold war, located right in the streets of Equestria. She didn’t really understand the powers arrayed on either side, didn’t understand their motivations, their magic, or the rules of their conflict.
If I don’t walk away from this, I might cause more harm than good. I might make things much worse without even knowing how.
But she could still see the twisted figure of the boatman, all wrapped in rags and leaning on his pole. “I was in the Underworld yesterday,” Twilight said again, abandoning all pretense of some clever twist in logic. “I spoke with the boatman. He doesn’t want you to die. If you do this… it feels like this is the moment.”
Rarity shrugged. “I don’t know that I believe in…” She cleared her throat. “Forgive my crassness, darling. I don’t mean to impugn your witness account. But just because I hunt one kind of dark creature doesn’t mean I can accept everything else about a world with no laws and no constants. Vampires are a disease, with symptoms that can be measured and perhaps cured. An Underworld, that is something different. Next I suppose you’ll tell me that I invite fairies for tea and the pale mare for dinner.”
I think you had her for dinner last week. But Twilight just kept her mouth shut. Rarity’s tone would brook no argument. “Suppose… forget about the source of the information. Imagine I tell you with absolute certainty this mission is going to get you killed. Do you turn around?”
Rarity sat back on her haunches, watching the mountain go by behind them. They’d left the switchbacks behind, and passed into the tunnel right before Canterlot’s main entrance. They probably weren’t expecting this train to arrive without a train. “That depends,” she eventually said. “Can you also tell me with confidence that my sister will not be cured as a result? Am I doomed to failure as well, or only to die?” She smiled ruefully, drawing her rapier and swinging it weakly through the air. “All mares die, Twilight. If my time comes fighting for the ponies I love, I can imagine worse.”
“Then… you’re not giving me a choice.” Twilight rose to her hooves. “I’m coming with you.”