Body Swapper

Type: Necromancer
Body Swappers are actually Necromancers who specialize in the complex process of replacing the soul in one body with that of the another, effectively trading souls (in the event of two living subjects) or merely transferring a disembodied ghost to the body of a living person. 
Body Swappers usually keep "collections" of souls of victims whose bodies are now 'piloted' by spirits, especially demons.