Since I'm not acquainted with 'The Jackal Thirteen Ghosts' story, I can just assume some general key elements. The number thirteen is often associated with superstition in Western culture, so the thirteen ghosts might carry that sense of foreboding. The jackal, being an animal, might be an unexpected element in a ghost - related story. Maybe it has some special abilities or characteristics that play a role in the story, like it could be a guide through a haunted realm or a victim of the ghosts' hauntings.
As I don't know the story well, perhaps one key element could be the jackal itself. It might be a central character around which the story of the thirteen ghosts revolves.