A dybbuk is a malicious possessing spirit, believed to be the dislocated soul of a dead person. These demons are said to have escaped from Hades, or to have been turned away from Hades for serious transgressions such as suicide, for which the soul is denied entry. The dybbuk attaches itself to the body of a living person and inhabits the flesh. According to belief, a soul that has been unable to fulfill its function during its lifetime is given another opportunity to do so in dybbuk form. It supposedly leaves the host body once it has accomplished its goal, sometimes after being helped.

Dybbuks are members of the Supernatural and Fantastic Wayfarers Association.

SOURCE(S): The Zork Chronicles