The town was a mess, as Twilight had expected it to be. Buildings destroyed or on fire, ponies running and screaming, and a number of unicorns teleporting around. Though not all of them seemed intent on destroying things. In fact, most appeared simply curious about their surroundings, looking around and taking stuff apart with their magic to figure out how it worked. A perfectly natural reaction, Twilight thought, given how long they'd been away from Equestria.
The destruction seemed to be mostly caused by a smaller group of unicorns. Some were blasting magic at the buildings, some were setting things on fire, some were launching objects around. Twilight caught sight of the black one who had spoken to Celestia before teleporting away teleporting between some of the more violent ones and talking to them. As she looked at the scene, she realised not all the unicorns who had come out of the box were there, and in fact the number of those present seemed to steadily diminish as they teleported away.
"Twilight, I think they're running away," Celestia said, feeling the irresistible need to state the obvious.
Twilight grunted and smacked a hoof against her face. "I can see that! Do something!"
Celestia looked at her, then walked to a nearby pile of rubble, sat down and began to pile rocks in order to build a small tower.
Twilight gave a wordless scream. "Something useful!"
Celestia stopped and turned around, still sitting. "Like what?"
"Containment spells! Call your guards! Issue some warning for the citizens! A list of the ponies we're looking for and what their powers are! Try to catch some of your students before they all run away!" Twilight's front hooves flailed desperately above her head.
"Oh." The alicorn got up, then teleported away. She reappeared a second after, the black metal box on her back, a group of armoured guards around her. A protective magical barrier rose over the city, and all citizens were teleported inside the still stable buildings as the barrier spread around them as well, while simultaneously pulling every unicorn that had once been her student out of those buildings. As it crept over the fires, the barrier extinguished them.
Twilight looked at her. "Oh. I... Thanks, I guess."
Celestia smiled. "I've trapped all the unicorns that were still in Canterlot here. The bubble will progressively shrink, and I've already ordered more of my guards to come help us. Luna is unfortunately away from the city. Now we just need to seal them back in here," she said, holding up the box in a hoof.
A black blast of magic hit the box, which fell to the ground and began to melt and twist and crumble.
Twilight looked at it, then at the unicorn who had fired the blast, now smiling to himself.
Celestia looked at the box. "Okay. Change that to now we just need to seal them... somewhere." She looked around. Some of her students were trying to destroy the barrier, others had noticed her presence and were slowly surrounding them. "Guards? In position," she commanded.
As soon as she'd spoken, the guards around them spread out in a circular pattern and readied themselves, unicorns raising their horns and charging spells, some preparing nets to throw to capture the fugitives. Celestia took her place amongst them, Twilight moving to stand at her side.
"So what's the plan?" the younger alicorn asked, magic lighting her own horn as she studied the unicorns slowly circling and observing them.
Celestia didn't answer.
Twilight looked up, to see the white alicorn was pursing her lips, gulping as her eyes nervously darted around. "You... don't have a plan, right?" the purple princess asked in a flat tone.
Celestia swallowed and gave a small cough.
Twilight exhaled, rolling her eyes. "Want me to help?"
One of Celestia's past students shot a blast, and Twilight narrowly managed to deflect it before it hit one of the guards.
"Well..." Celestia began.
Twilight donned an unamused expression. "Could you at least tell me what we're up against? You're the one who's supposed to know what each one of them can do."
Celestia gave another brief cough. "Yeah, about that. So, let's see." She lifted a hoof and began to point at the unicorns surrounding them. "That one freezes things. That one shoots lightning. That one has a great talent for mixing drinks. And also telekinesis, I guess. That one I'm not actually sure, something to do with ants I think? That one's got a great singing voice, and-" Her mouth was sealed shut by Twilight's magic.
The purple alicorn took a series of deep breaths to calm herself down. "Okay, listen here, everypony," she spoke to the guards. "The most important thing is making sure they don't band together. We might be even able to talk to some of them, but if they start working with each other we'll never beat them. Celestia, can you use the same containment spell you used for the box?"
Celestia shook her head. "I'd need time to find an appropriate container to enchant," she explained.
"Then we'll have to catch them individually. Are the nets anti-magic?"
"Yes ma'am!" one of the guards replied.
More and more unicorns moved towards them, some simply curious, some ill-intentioned, some willing to go as far as needed to escape from the containment barrier.
Twilight blinked once, trying to concentrate. "Let's see. First thing first we should-"
All the guards around them fell asleep on the spot.
Twilight looked up to see a grey unicorn sliding away behind a building. Her eyes flashed to Celestia. "You had a student who can do that? And you didn't think about bringing it up? And you brought in guards when you knew that would happen?"
Celestia rubbed the back of her neck with a hoof, teleporting all the sleeping guards away.
Twilight looked back at the unicorns surrounding them. "Well, at this point-"
The barrier shattered. As soon as it did, almost all unicorns teleported away, disappearing completely from their sight. Rain reached the ground, and Twilight felt it sting on her skin, magic clearly infused in it. The ponies inside the buildings fell asleep too.
The only unicorns left were the black one who had spoken to Celestia, and a purple one he was now whispering to. The black one finished talking, then teleported away with a last look at Twilight, leaving only the purple one behind, horn pointed at the alicorns.