When they walked out, they left the previous lead of their group with a very sour taste. So, that person wants to destroy the main’s new group, as some kinda convoluted plan to try and get them back in.
So yeah, they decide to turn people to stone and erase them outta existence.
It was more like a falling out of ideals, and at the time. The main is struggling to identify as themselves, since their previous life and their current experiences shaped them in a different way, which affected their skill set.
So yeah, they decide to turn people to stone and erase them outta existence.