The copyright remains with them. It's only the Holy Grail of the genre.
Many movies strive to be as dark, unnerving and stylistic and most fail.
As the killer dies, his soul floats out of his body into an unsuspecting prison guard. And wouldn't you know it, the more he finds out about this travelling soul, the more he realizes that it will be impossible to stop it. It's dark and somewhat stylistic, but not quite unnerving. And there's a very impressive scene where the soul is chasing Milano down a busy sidewalk, flinging itself from host to host in an attempt to catch her. Most of the best acting actually comes from the people who briefly host the demon soul.