He has schizophrenia where he hallucinates the brother he murdered. He killed everyone in his au to gain exp to kill the human named frisk who has a determination soul. This skeleton is edgy and doesn’t feel much emotions but can be quite friendly when he isn’t being murderous. He likes to do pranks and is part of a Undertale au group called “bad sanses” with killer and horror, their boss being called nightmare. They are pretty powerful and backs down from challenges that are too hard for him.