The power to transfer souls from their original bodies to others gaining its abilities and powers. This usually requires that the soul o the new body has already passed on but incredibly powerful souls can override host's control. These bodies eventually start decaying and "burn out" and become nothing more than animated corpses before it has to be disposed of. For if they body dies while the soul is still in it the soul dies as well. The stronger the body the longer it last. This can also be used to subjugate an existing soul sealing it in the body to keep it alive. However the soul and body have to maintain constant balance limiting the amount of time the body can exert itself physically. This process can also be reversed i.e someone using their own body to seal an evil soul. This approach does require a physical seal and if that seal is broken the soul takes control until the seal is reapplied. Though they share the same body the two souls have separate reserves of energy granting the vessel a sort o super powered evil side.