In a hallway in Canterlot High School on an average school day, a lavender-skinned girl with violet hair wearing a stunning dress suddenly let out a primal scream, shot down the hall like a comet, and slammed her fist into the face of a muscular, red-skinned teenage boy while an almost identical lavender-skinned, violet-haired girl wearing a school uniform and black-rimmed glasses stared in wide-eyed shock.
"TIREK!" Princess Twilight Sparkle screeched as she flailed away at her quarry with fists and feet. "YOU! MONSTER! I WON'T...LET YOU...again..." Suddenly, she sank to her knees, all the energy and fury draining out of her body. She panted heavily, then turned a murderous glare up at the boy, who was staring down at her with a bemused expression. "Monster," she hissed.
Six girls materialized around her, lifting her gently to her feet and supporting her. They were torn between checking on her with concern, staring at her doppelganger with wonder, and shooting suspicious glares at the boy she had just assaulted out of nowhere. All around them, other students had stopped in their tracks and were watching, whispering and murmuring.
"Twilight, are you okay?" Sunset Shimmer asked worriedly, checking her friend over. "What just...what just happened?" She glared suspiciously at the red-skinned boy. "What did you do to her?"
He scowled. "I have done nothing to her," he rumbled.
The other Twilight finally found her voice as she stepped forward, adjusting her glasses. "She really does look just like me," she said. "She even sounds like me. Except I've never been that, well...shouty..."
Suddenly, Princess Twilight seized her counterpart by the shoulders and shook her. "Twilight! You have to listen to me! You can't...don't trust him! Stay away from him! He's pure evil!"
Twilight frowned, disengaging herself. "Excuse me," she said coolly, "but right now, the most suspicious person here is you. Tirek looks and sounds scary, and maybe he has a bit of an...intense personality, but he's been nothing but respectful and helpful to me and Dean Cadance."
Dean Cadance, for her part, snapped out of her shock and confusion at the unexpected display and cleared her throat. "Would anyone care to explain why this girl assaulted one of my students and possibly caused a diplomatic incident?"
"I'm rather curious about that myself," a new voice intruded. Principal Celestia cut through the crowds, her face stern and all-business. She regarded the two groups facing off against one another, her face registering surprise at the presence of two Twilight Sparkles. "Explain," she snapped in Sunset Shimmer's general direction.
Sunset sighed. "Twilight—our Twilight—came back to help with our little problem," she said. "This other Twilight is this world's Twilight, and she goes to Crystal Prep. I recognize Cadance here, but I have no idea who this guy is, or why our Twilight just completely freaked out when she saw him."
"Because he's a monster," Princess Twilight said. "He almost destroyed Equestria. I have no idea how he escaped Tartarus or what he's doing here, but—"
"Uhh, Twilight?" Sunset interrupted. "D'you think maaaaybe he's just, y'know, this world's version of whoever you're talking about?"
That took the wind out of Princess Twilight's sails. Her eyes widened. "Oh," she said quietly. She blinked, then looked from the other Twilight to the scowling Cadance, then to the contemplative Tirek, then to a visibly angry Celestia. Her shoulders slumped. "Right. I...I'm sorry." She took a deep breath, sighed, then glared at Tirek. "But I still don't trust you," she said. "Twilight, Cadance, you shouldn't trust him either. What are you even doing with him?"
Principal Celestia clapped her hands loudly. "Alright everyone, get to class!" she yelled. "Right now! Not you, Sunset," she added. "You, Twilight, the other Twilight, and you two, come with me."
"But—" Rainbow Dash started.
"CLASS," Celestia said sternly. Her eyes softened. "I know you're involved in this, but right now the fewer people shouting over each other, the better."
Rainbow sighed. "Fine." She glanced at her friends, nodded, and skulked off to class. The crowd in the hall dispersed slowly.
"We'll see you two later," Fluttershy said as she passed, giving Princess Twilight's shoulder a squeeze. The other Rainbooms expressed similar sentiments of encouragement as they drifted off to their own classes.
Soon, it was just the two adults and four teens. Principal Celestia regarded Dean Cadance coolly, affording her a respectful nod. "Cadance," she said.
"Hello, Celestia," Cadance said a bit sheepishly. "Umm..."
Celestia held up a hand to stall her. "Not here." She marched crisply down the hall, making it clear everyone was to follow her. Glancing around awkwardly at one another, the rest of the group followed.
Princess Twilight cast a glance at the glowing, chiming crystal around Tirek's neck. "You have magic," she said quietly. "Magic that shouldn't exist in this world."
"I could say the same of you," Tirek rumbled. "The two of you clearly possess incredible magical power."
"Oh, you have no idea," Princess Twilight said with a dangerous, menacing chuckle. "And since I'm not stuck in this form this time around, you REALLY don't want to make me angry."
"Twilight," Sunset said in a warning tone.
"What do you mean 'stuck in this form'?" the other Twilight asked, glancing at her doppelganger curiously. "And why are you stealing my face and my name?"
"I'm not stealing anything from you!" Princess Twilight retorted. "I am Twilight Sparkle!"
"That's funny, because I'm pretty sure I'm Twilight Sparkle," Twilight countered tartly. "Says so on my birth certificate, my student ID, my—"
"Okay, both of you, enough," Cadance said wearily, massaging the bridge of her nose.
"Sorry," both Twilights said at once. They glanced at each other, frowned, and looked away.
Sunset facepalmed. "Way to make a first impression," she muttered.
Celestia led them to a conference room. Once they were all inside and seated, she sat down at the head of the table and folded her arms. She gave Cadance a hard stare. "You first," she said.
Cadance sighed. "Twilight, Tirek, and I are investigating the..." She frowned. "Well, it's..."
"There is magic at this school," Tirek said brusquely. "Twilight detected it. We came here to study it after discovering similar magic at Crystal Prep."
Princess Twilight groaned. "The backup portal," she said, covering her head with her arms. "This is all my fault..."
"So, you created that portal in the girls' bathroom," Tirek said. "Interesting."
"How...?" Twilight asked, staring at her counterpart.
Celestia held up a hand. "So you thought it'd be okay to bring two students from your school here to poke around, without consulting me?"
Cadance winced. "I, umm...I did clear us being here with Luna," she said. "I just...didn't tell her the real reason. I said we were studying student culture here."
Celestia raised an eyebrow. "Alright. We'll discuss that later. More importantly..." She glanced at Tirek. "That glowing crystal."
"A relic passed on to me by my mentor in my homeland," Tirek said. "It detects sources of magic." He snorted. "It's detected quite a lot of it recently."
"Something that dangerous shouldn't be in your hands," Princess Twilight said.
Tirek frowned at her. "You continue to judge me when you do not even know me," he said. "It grows tiresome."
"Yeah, quit picking on him!" Twilight said. "We have no reason whatsoever to trust you!"
"What is your problem with this guy?" Sunset asked curiously. "I've never seen you freak out like that."
Princess Twilight scowled. "Tirek came closer to destroying Equestria than anyone ever has," she said. "Nightmare Moon, Discord, even King Sombra...none of them came anywhere close to his level of carnage."
"Equestria?" Twilight asked, tilting her head.
Sunset frowned. "Okay, I know I haven't been home in a really long time and I may be a little rusty, but I think I'd have heard of something like that."
"It happened a few months ago," Twilight said. "Tirek escaped Tartarus after over a thousand years of imprisonment. He stole pony magic. First he went after unicorns. Then pegasi. Then earth ponies." She bowed her head. "Then he came after the alicorns. Princess Celestia, Princess Luna, and Princess Cadance all transferred their alicorn magic to me. It was the only way to protect all the alicorn magic in Equestria...to stop Tirek from taking it and dooming Equestria."
Dean Cadance blinked. "Princess Cadance...?"
Tirek rubbed his chin. "I believe I'm beginning to understand," he mused. "Dean Cadance, you mentioned seeing a pink horse come out of that mirror. One who looked like you and spoke to you."
Cadance nodded. "Yeah..."
Tirek looked between the two Twilights, his eyes narrowing. "Yes. I do understand," he said. "The portal connects to a parallel world. A magic world, where there are counterparts of people here."
Twilight gasped. "That...! That explains so much..."
"Yes," Princess Twilight said in a steely tone. "And your counterpart hurt my friends and destroyed my home. Tried to KILL me to get all the alicorn magic in Equestria. So you'll understand when I say I have very good reason to distrust you."
Tirek nodded. "Were I in your place, I would likely have the same reaction," he agreed. "It is sensible to be wary of me when my counterpart has caused you such grief." He stared into her eyes. "But understand this. I am not the Tirek you know. I am not your enemy. I merely seek...an understanding of that which, to this world, is fantastical and unknown."
"I'm after the same thing," Twilight said. "I want to study this magic and understand it. I...I need to know."
"What worries me is what you'd do with that knowledge," Princess Twilight said. She glanced from Tirek to Twilight, then added, "Both of you."
Twilight blinked. "Both of...? You don't trust me?!"
"If you're anything like me? You mean well, but you'll get too caught up in what you're doing, get in over your head, do something stupid, and..." She made a vague 'explosion' gesture with her hands.
Cadance giggled. "That...does sound a bit like Twilight," she said.
Twilight blushed. "Dean Cadance!"
"And honestly, right now isn't the best time to have you poking around," Princess Twilight continued. "We're having...a bit of a problem."
"What kind of problem?" Twilight asked.
Princess Twilight frowned hesitantly. Sunset touched her arm. "She might be able to help," she said. "I mean, you never know."
Princess Twilight sighed. "There's too much Equestrian magic in this world," she said. "It's screwing up the balance of magic here. We're trying to figure out exactly what the source of the imbalance is and how to fix it. There are a couple of probable causes, but the most immediate cause is a problem with our original portal to this world. It's no longer functioning properly, and one of the safeguard spells Starswirl the Bearded built into it has failed. Sunset..." She frowned.
Sunset grimaced. "The portal's supposed to turn you into a human when you cross into this world from Equestria," she said. "A few days ago, I woke up in my original form. Twilight had to figure out a way for both of us to appear human in this world, but it's temporary and takes a lot of magic to maintain."
Princess Twilight nodded. "We created a second stable portal that opens up at your school so I could come across and try to figure out what's going on and how to restore the natural magical balance of this world."
Tirek raised an eyebrow. "So your idea of correcting the flow of magic from your world into this world is cutting open another wound for your world to bleed from?"
"That we can collapse without incident if it makes things worse," Princess Twilight said a bit hotly. "Besides, it was necessary so I can determine if the portal here is what's causing the imbalance in the first place."
"See, the portal at this school is only supposed to open once every thirty moons," Sunset explained. "On its own, it opens for three days every thirty moons, then closes. But when we had some...trouble here not long ago, we needed help from Equestria, so Twilight found a way to open the portal and keep it open."
"And that might be the problem," Princess Twilight finished, grimacing. "I mean, it's not like we're just leaving the portal open all the time, but we have a way to force it open that bypasses the original spells Starswirl used in its creation."
"So you hacked it," Twilight said, adjusting her glasses. "And you introduced a bug into the source code."
"That's a good analogy," Sunset agreed.
"And now we need to figure out if that's what's causing the problem," Princess Twilight said. "If it is, then I'll need to find a way to fix it without collapsing the portal entirely. We...really want to keep it open if we possibly can."
"Because if we can't, then every source of Equestrian magic has to be removed from this world," Sunset said with a heavy sigh. "Including me, and I don't really want to leave. This is my home now."
"And if it isn't the cause?" Cadance asked.
Princess Twilight shrugged. "Then we'll need to examine every person and every thing in this world that's either from Equestria or has been touched by Equestrian magic, and that...could take a while."
"Yeah, especially if we don't know how many problems Starswirl tossed through that portal," Sunset said with a roll of her eyes. "Honestly, after the Sirens, I'm wondering if he didn't make that portal to be Equestria's magical garbage disposal."
"I think that's pretty much exactly what it was meant to be," Princess Twilight said with a pained grimace.
"What, you don't have dungeons or prisons in your magical world?" Twilight asked, arching an eyebrow.
"We do," Princess Twilight said. "And we even have ways to suppress magic. But some threats are too dangerous even for Tartarus. Or at least, that was the case back when the Sirens were around."
A silence fell as the group from Crystal Prep digested everything they'd heard.
"If you can't fix this magical imbalance," Cadance asked slowly, "what does that mean for this world?"
Princess Twilight grimaced. "We don't know," she admitted. "But I don't want to risk having to find out."
Tirek and Twilight exchanged a glance. Twilight took a deep breath. "We want to help you," she said. "But in return, we want to know everything. About magic, about your world...all of it."
Princess Twilight frowned. "I...don't know..."
"Wait," Sunset said, holding up a hand. "Twilight," she began, addressing the human Twilight, "how did you even know about the magic here at CHS in the first place?"
Twilight pushed her glasses up her nose. "I have a lab full of sensitive measuring equipment," she said. "Seismographs, EM frequency and radiation detectors, pretty much everything to measure everything. Everything that's been going on over here over the last several months has been generating bizarre readings on all my equipment. It took me a while to create a custom tracker that would measure the specific frequencies of energy and particle emissions this...magic is creating, but now I can scan specifically for magic and filter everything else out." She frowned. "Or I could until you two shorted out my tracker."
"She's a genius with electronics and gadgets," Cadance said with a hint of pride.
Sunset raised an eyebrow, then turned to Princess Twilight. "Could be helpful," she said.
Princess Twilight sighed. "Alright," she said. "You can help, and...and I'll answer any questions that are safe to answer."
"I'm glad we settled that," Principal Celestia said with a tired sigh.
"The first question I have," Twilight said, holding up a finger. "I want to know exactly who and what you are." She fixed a stern gaze on Princess Twilight. "If we're dealing with parallel worlds here, I'm gonna assume you're another version of me, but I need to know."
"You did mention the two of you are not human," Tirek pointed out. "I admit to being curious about that point."
Princess Twilight and Sunset glanced at each other nervously. Sunset gestured vaguely with her hand. "You're the alicorn," she said. "This one's all up to you."
Princess Twilight sighed and stood up, slipping off her shoes as she did so. Brushing aside her hair, she pulled the glowing crystal amulet out of her dress, then unfastened the chain and dropped the still-glowing amulet onto the table. A bright magenta glow suffused her body, and a blinding white flash filled the conference room, forcing everyone to cover their eyes.
As the light faded, her empty dress and underwear pooled on the floor. The native humans looked on in stunned awe at the small yet majestic equine suspended in midair, slowly gliding to the table surface on massive, feathery wings.
"I am Twilight Sparkle, the Princess of Friendship," she said as her hooves touched down. "One of the four alicorn princesses of Equestria."
Tirek's crystal let out a loud, sharp sound and shattered.
"And I am Magic," Princess Twilight added with a smirk.