"You can back out," Sunset said. "All of you. You can just leave now. Go on with your lives, not... not know what's here."
The other teenagers gave her a series of flat looks.
"Speaking as the one who is, semiregularly, possessed by Magic when things get out of control," Twilight said as she calmly adjusted her glasses, "I'd like to know if whatever's going on here could affect me in any way whatsoever."
"And speakin' as yer friends," Applejack added wryly, "Ah think if'n whatever's in there has got yer heart in a twist, we should know what's goin' on too. Mister Discord does, right?"
"Mister Discord, Celestia... the president..." Sunset wrung her hands. "Adults, guys. They're all... they needed to know. But that doesn't mean you do."
"So, is this a secret because you're ashamed of it, because people would panic if they knew, because the more people know the more dangerous it is, or because we're going to be exploring the dark side of human psychology?" Pinkie asked.
Sunset winced. "...all of the above."
"Ooooooo. Yeah, hmm. No, you don't get to carry this burden alone."
That got a laugh out of Sunset. "I'm not! I'm not, I swear. Like I said, there are people on the need-to-know list, and that actually does include psychiatrists, guys, I do have people I can talk about this with--"
"Are they your friends?" Fluttershy asked quietly.
Sunset bit her lip. "...they... maybe. They might... become friends."
Rainbow rolled her eyes. "Okay, look. I'm awesome, so--"
"Rainbow," Sunset said flatly.
"What? I am!"
Sunset looked around. "Anyone mind if I cast a truth spell on Rainbow? False bravado is not allowed inside."
"What?!" Rainbow held up her hands, even as the others all murmured their agreement. "I don't do false bravado!"
"This is for your own good, Rainbow. If you're coming in, you're getting the spell."
"But--"
"That's the condition."
"....Only if everybody else has to too!"
Rarity frowned. "This spell... it's not 'forced to speak the truth in blunt terms,' is it?"
"More like 'cannot tell a lie,'" Sunset assured her. "And it does let you pick your words."
"Oh, good. In that case I'm alright with it."
"Remember everybody," Pinkie said, "if you can't say anything good, don't say anything at all!"
Sunset gave her a wry smirk. "Then you'll be very quiet through this whole trip." She rose her hand, letting a light descend on all of them. "That's going to last for the next ten minutes, or until I decide to dispel it."
"You cast it on yourself," Twilight noted.
"Yes. Because... because I want you to know, for certain, that what I'm saying is something I absolutely believe: I don't want you knowing about this. I'm worried you'll have nightmares for weeks. Or worse. What's in here isn't... isn't..." She frowned. "Okay, some of it is pretty, in an aesthetic sense, but from a moral standpoint it's very distasteful. Huh. Might have made the spell a little specific there..."
"At this point, I'm honestly more irritated that you're hiding this than I am worried I might be traumatized," Twilight deadpanned.
"Yeah!" Rainbow agreed. "Let's get this crazy-train moving!"
Sunset frowned pointedly.
"Wow. That sounded rude, didn't it." Rainbow shrugged. "I'm... I'm... okay, why can't I say it?"
"Because you don't feel regret and just want to assure Sunset you didn't mean to be rude?" Pinkie suggested.
"Yeah, if'n this is how it is, Ah'd be more comfortable if you toned down the strength there." Applejack nodded to Sunset.
"Alright." Shutting her eyes, Sunset concentrated for a moment or two. "It should be good now. Rainbow's right, though. If you're all absolutely sure I can't convince you to turn around..."
"Nope. We pooled our resources to figure out what's got you so stressed, and all evidence says it's in that warehouse."
"...Let me just signal the guards." Sunset pulled out her phone, tapping the screen. "And... I want you all to know, if there was any other way, I'd take it. Right off the bat."
She led them, somberly, to the gates of wire and barb, nodding to the armored men standing on either side as they slowly swung open. The rumble of air conditioners, and the clip of patrolling boots, spoke of a well-maintained and well-guarded facility, though warning signs in multiple languages were scattered about the walls and demanding that any intruders turned back. A few cards on ribbons floated from a guardpost, landing in Sunset's hand; she passed her palm over them, before handing them out to her friends.
Rarity glanced up from hers. "So, what do these let us access?"
"They say you're with me for the day, and beyond that you aren't allowed to wander. Stay close." Sunset pointed at Pinkie and Twilight. "That means you two as well. Understand?"
"Of course!" Pinkie nodded vigerously. "I won't let you down!"
"I know how to... mostly control my curiosity." Twilight frowned. "This spell is a bit annoying."
"A bit annoying." Sunset nodded. "Magic can be that way."
She led them toward the large warehouse in the center of the fenced off region, and stopped in front of a pair of massive doors with the faded image of an airplane. The girls looked around, noticing a squad of guards around them; notably, they faced inward, toward the building itself.
"I assume you've heard stories of people getting bursts of superhuman strength," Sunset mentioned suddenly. "Adrenaline rush in times of danger or anger, doing things that would be impossible, pushing themselves beyond their limit."
The doors slowly slid open.
"And I'm sure you've noticed that magic can be affected by the emotions of the caster."
"Wait, hold on." Rainbow narrowed her eyes. "I think I know where this is going..."
"I think I do too," Rarity murmured. "Sunset, have you... have you been capturing people?"
The doors jolted to a stop. Sunset's shoulders sagged, for a moment or two.
Then she straightened and walked in.
"Equestrian magic," she began as the others followed her, "is fundamentally resonance based. It factors into our biology, our society, our culture; you have to convince what already exists that it wants to act in certain ways. When a foal is in the womb, their developing magic field affects their body; you almost never hear of transgenderism or transtribalism because, well, it's your own magic that shaped your body, into as comfortable a vessel for your soul as you could have. We're not as well equipped to handle actual genetic problems, though. And mental magic, it's... a part of the mind has to want to be affected by the spell, or the spell won't take, so doctors use it in place of a number of drugs."
The girls jumped as the doors groaned to life again.
"Of course, as with drugs, it's possible to overdose and end up going off the deep end. A lot of old dark artifacts are emotional amplifiers. A lot of dark spells..." Sunset shut her eyes. "A lot of dark magic, really, is about losing yourself to the resonance. Of love, or of hate. Surprise or fear. Joy or sorrow. When you let one dominate, your magic becomes more powerful, but it also takes... certain shapes."
And with a massive clang, the doors were shut again.
Twilight looked around the well-lit warehouse, at the various chambers set up and monitored by scientists and guards. "...What about Earth magic? It's different, right?"
"Oh, yes. It's not resonance based." Sunset shook her head. "I don't know what it is, exactly, I'm still figuring it out, but... Earth magic seems to impose the caster's will more easily, and have more resistance from that which exists. But that's not the problem here."
Fluttershy squeaked. "What... what is the problem?"
"There wasn't magic before." Pinkie's voice was flat. "Or at least, not obviously. We could let our emotions run wild without thinking of the consequences."
"Or emotionally abuse each other." Sunset led them to one chamber, gesturing at a small screen. "This man, he's from Tauros."
There was a sharp intake of breath.
"Yeah. Minotaur aspect. I don't know if he was a psychopath before, or if his magic warped his hatred into a physical force... He was part of an ethnic minority, oppressed by the government, and he made a sword that cut through anything. Numerous terrorist attacks. Didn't work like he planned, Tirek actually used his actions as 'evidence' that magic needed to be controlled by the government..."
"Wait, Ah remember that." Applejack frowned. "That was way back before Tirek became tha monster we all feared. Didn't half a dozen people die...?"
"Yeah. His actions led to Tirek taking power, and then..." Sunset sighed. "Even with that, he wouldn't have been put here, but after Tirek was deposed I found him running around, killing people and screaming... he was a threat that couldn't be talked down. So I bought this place and negotiated a deal with the government."
Twilight took a breath. "I remember... I was talking with Lemon Zest, and she said you helped Sour Sweet when her magic was influenced by her... schizophrenia. Why couldn't--"
"Schizophrenia," Sunset said calmly, "is an imbalance in the brain. It's chemical, it's diagnosed, it... yes, I helped her. Because, well, I knew what could help. I couldn't cure her, but I could affect her magic so it wouldn't be as violent in the future, and I could spread the knowledge around. This?" She pointed at the chamber. "This is hatred. No chemicals, no brain imbalances, purely in the mind. I can't help him. I don't know how."
"...He's not the worst here," Rainbow said, her voice unusually somber. "Is he?"
"No." Sunset shook her head. "The worst I've encountered... she's in a cement chamber, thirty feet below us."
Fluttershy bit her fingernails. "Why?"
"...Abuse victim. A seven year old abuse victim. Physical, psychological... sexual... I'm not telling you where I found her, only that she was being trained to be... used. She got the unicorn aspect, she saw my message and... it took seven months for her to realize what she had." Sunset shook her head. "Her magic... when I noticed it flare, I transported there instantly, and it was already Tartarus. I barely managed to contain it. She's a walking Chernobull, leaking radiation like a sieve, and that's on top of the dark fire..."
She gripped the screen, leaning over. "The worst bit. The worst bit is that most of these people are victims. Victims of extreme situations, reacting with extreme emotions, and the magic is... running out of their control. What you've seen, what's hit the news, that's nothing to what I have here, but if I just... if I just kill them... it's not their fault, not entirely. They've lost control. And I'm not sure what to do with them."
For a moment, there was silence.
Then, Twilight coughed. "You helped Sour Sweet."
"Yes."
"You... seem to have scientists studying these people."
"Mostly mister Discord's folks, though I did vet them."
"I think," Twilight said slowly, "that what you're doing here.... it's the best you can do. Secure them, so that they don't cause any more trouble. Contain them, so they can be studied. Protect them, so they can be helped. So long as everyone involved agrees these are people... I think this is the least of all evils."
"...I know. But..." Sunset looked up. "I just... wish I could do more."