When you deal the killing blow to this enemy, its haunting spirit escapes from the corpse and screams into your body, roll+WIS. On a 10+ the spirit has a tenuous grasp on you, it will trouble your dreams. On a 7-9 the same, but the spirit also haunts your waking life and will occasionally speak to you. On a 6- the spirit might briefly take control of you during moments of weakness. The spirit will stay with you until an appropriate ritual is performed to expel it.
This one comes from my recent rewatch of Supernatural. I like that this move is all fiction and not mechanics. One thing I’m not sure of is the 6- result. Having something take control of you might be too much, so I’m considering changing it to the spirit can affect the world around you like a poltergeist. This gives you a neat move to make on failed roll at least.