When a demon (or any other invading, mind-controlling force) possesses someone, it can get pretty nasty. The host will have no control over their actions, they'll be forced to do the demon's bidding, or even fight their former friends. It's not a pretty picture... ...unless, that is, the demon and its host are pals. Whatever the case is, the two become less of a parasite and host, and instead two beings who view each other on equal ground and are willing to pass control of the body between each other when the situation calls for it. Examples of Symbiotic Possession include: