Nightmare used to be a sweet kind hearted man, but hes changed. He got bullied for being the guardian of negativity. So he got tired of it and ate the black apple to get stronger. That was a mistake, he ended up getting black goop all over his body and over one eye. He was no longer your best friend. He hated you, for some reason.. you don't know what you did wrong. He despised you. You ended up hating yourself over thinking about what you did wrong, you started harming yourself as punishment. He liked seeing people in pain, it gave him power, You stod in your room holding a picture of him from the past. What were you gonna do now that he was gone?