Demonic possession is held by many belief systems to be the spirit possession of an individual by a malevolent preternatural being, commonly known as a demon. Descriptions of demonic possessions often include erased memories or personalities, convulsions, “fits” and fainting as if one were dying. Other descriptions include access to hidden knowledge and foreign languages, drastic changes in vocal intonation and facial structure, the sudden appearance of injuries or lesions, and superhuman strength. Unlike in channeling, the subject has no control over the possessing entity and so it will persist until forced to leave the victim, usually through a form of exorcism.
Many cultures and religions contain some concept of demonic possession, but the details vary considerably. The oldest references to demonic possession are from the Sumerians, who believed that all diseases of the body and mind were caused by "sickness demons" called gidim or gid-dim. The priests who practiced exorcisms in these nations were called ashipu as opposed to an asu who applied bandages and salves.