In my fantasy novel, the main Antagonist is a King, who is also host to a spirit. This spirit wishes only for one thing: to find a specific amulet, which is required for him to achieve his full power. The King, who is merely a host, has an internal struggle against this spirit, which is unfortunately too strong. This just seems too one sided, too black and white. I don't want the spirit to be "just evil", but then again I don't see how I can make him not.