Is this a good anime idea? Or does someone else already have it?
A fallen angel who got kicked out of heaven for sin in his heart seeks revenge. So instead of letting the souls of the dead pass through their door into an eternal rest, he created a dark key to lock the door, forcing the souls to stay on earth and cause mayhem. He is the "Door Keeper". He also is in charge of sending the souls into hell for Lucifer to decide if they shall become imps or other Door Keepers. Is this a good idea or does someone else already have something similar?