Ghost

Ghosts are the restless spirits of those unable to find peace in death. They are incorporeal undead who usually manifest themselves as translucent figures, often shimmering blue with twisted facial features. They are always bound to certain places, normally linked to their physical remains or the event that caused their premature death. 

Ghosts almost always have a specific problem that needs to be solved for them to find eternal peace and leave the living alone. It may be a matter of revenge or a debt that must be paid; other times the ghost’s remains must be collected and given a proper burial.