Why did lucifer turn evil?

hmmm...not exactly sure (if you want to be absolute sure read The Bible or whatever) but I think it's because he was God's brother or something and God decided to create humans and said that he had to love them. but lucifer didn't want to or he was jealous that God loved us more than him so he became evil and was cast out of heaven. (I think the story goes something like that- even though that's just a short summary) ^^