Your father's in here with me. Trapped inside his own meatsuit.
~ Azazel when possessing John Winchester.
Villains who must possess others to interact with the world or those who simply possess others for fun; even those who possess inanimate objects to attack their enemies can apply.

Often, possession is the tool of sealed evils from the past looking for a link to the world. Possession affects both victims of the Possessors' malevolent acts and the hosts themselves, who all too often have to live with the evils they have been made to commit.

NOTE: not to be confused with Brainwashers.