A Villain attack!

A large crowd of people emerged from the black cloud, evidently some kind of portal. Three figures seemed to be in the lead. The first was a figure that seemed to be made of that mist, with an odd neck brace, and glowing yellow eyes. The second was a massive, hulking monstrosity that had wide, unblinking eyes that conveyed no emotion, black skin, an exposed brain, and a beaklike mouth. The last was a spindly looking man with messy grey hair, pale skin, and, most distinctive of all, a macabre assortment of what looked like severed hands on his body, including one essentially gripping his face like some sort of mask.

"... that's peculiar... There's more people here than expected..." the last man mentioned in a raspy voice, scratching at his neck in what seemed like a peculiar gesture of frustration. "...and yet, not a one of them is All Might..." He turned angrily to the one made of the black mist. "Kurogiri... Did you steal the wrong schedule while those media pawns were providing the distraction?"

"Calm yourself Shigaraki..." the mist man, apparently Kurogiri, responded. "It's entirely possible that the plans simply changed since then."

"...tch, you're right," Shigaraki conceded, before turning back to the students and teachers.

"Who are all of you?" Aizawa asked, tightening his grip on his weapons.

"Apologies for the intrusion," Kurogiri replied, an air of menacing politeness in his demeanor. "We are the League of Villains. And we are here today to issue a declaration of war. By killing an entire class of students, and the Symbol of Peace."

The what he had said, and sheer nonchalance of the delivery, chilled Izuku to the bone. Worse, the sheer implications. The idea of killing All Might, the strongest Hero to ever live? This meant that the people were either insanely overconfident... Or they actually were dangerous enough to have a shot at pulling it off, or had a solid plan. And Izuku didn't dare to assume it was the former.

"Students! Get back to the buses!" 13 shouted, but that turned out to be a futile endeavor, as the villains had clearly come prepared, and had hacked the security systems, triggering the shutters, which covered the windows and all the exits, sealing them inside. To make matters worse, none of their cell phones were working. They were being jammed. This only further served to solidify Izuku's fears that they weren't dealing with amateurs. These people knew what they were doing.

But... They also clearly were afraid of more pros getting involved. And Izuku came up with a quick, **** plan to scare them off. He quickly turned to Tooru, who was currently visible. "Hagakure! Warp out of the building and get the police, and every pro you can!" he shouted, making the Villain's eyes widen, not having planned for a Warp Quirk like the Kurogiri's to be in play.

This also confused a good number of Izuku's classmates. "Eh? But that's no-" Kaminari started to say that teleporting wasn't Tooru's Quirk, before Jiro, having figured out what Izuku was trying to do, stomped on his foot, wordlessly telling him to shut the fuck up before he blew it.

Tooru blinked in confusion, before her eyes widened. "Got it!" she nodded, before swiftly turning herself, clothes and all, invisible.

"Shit! No!" Shigaraki cursed, scratching at his neck furiously. "That's not fair! Teleporting Quirks are supposed to be rare! It's cheating for them to have one too! We need to abort, and-" he was cut off from telling Kurogiri to get them out of there by another villain, this one with a shark like Mutant Type Quirk, stepping forward.

"It's a bluff. I can still see the girl's bioelectricity. She's still there, merely invisible," he growled, making Shigaraki pause, and then relax.

Izuku proceeded to mentally curse up a storm that would have quickly bankrupted him had he said it aloud in class. Shigaraki turned towards where Izuku was standing, and started to chuckle. "Well... Seems we've got a smart aleck... Perhaps we should kill him first..."