Isiah didn't want to stay there inside of the transportation center looking at Xavier's qs he was trying to heal their only way to level up.
He knew that considering all that happened there it would take so much time, so he just walked away after he threw so many threats .
He was not on a level that forced him to be patient with people's nonsense, after he got the necessary powers for leveling down he just was much stronger than everyone in this region and probably so many regions above.
The moment he cast the summoning spell for the portal that transported him, Isiah realized that he could do anything he wanted .
He improved a lot after leveling down, at least now he has enhanced senses that allow him to feel the energy from a huge distance.
Basically, that was not the only thing he could do with his powers, those dark powers were related to destruction and that is the only limit he could spot right now.
