The magical stones!

Katsuki Bakugou was the last surviving UA student in class 1A he was severally injured and traumatized but he was sent to another Dimension by Kurogiri's out of control quirk he wasn't the only one who was nomus and some villains were sent over as well

he wasn't healed in any way he still had his quirk but a lot more powerful and effective, Katsuki Bakugou was found by a phoenix who tells him everything about this world and tried teaching him more uses with his quirk and turned out to be working but the phoenix was hit with magic from a black colored stone

Katsuki was the only student with the fire stone from a phoenix because of that he was accepted into a school of magic users as no one heard of him before many students are suspicious and are overlooked by the principal who has his eyes on him

soon a huge problem happened a couple of students are going missing and it was his mission to find out what's happening with them he is quite powerful and attractive that makes him a good target

he does discover it and easily defeated it but it also provides proof to the principal that he was the strongest one there and chooses him as the representative of their school for the infamous tournament at the end of the school year

he was taken out of his classes everyday until the tournament where the top students out of every school would be selected to be trained by any chosen creature of the magic but something happened the tournament was under attack by the Nomus and black stone users

only the strongest ones stayed after helping the people escape Katsuki had defeated a good lot before the others got there to help the Nomus and black stone users had fell back the schools were also attacked none survived, out of the schools but the fire as Katsuki actually ran into the fire only to find dead bodies as well as the principals one but he did grab a school photo and a potion that he drank as he thought it was water but it made him more like his creature who trained him