Gidim (etemmu in Akkadian) are the Sumerian equivalent of ghosts; they were the spirits of dead people living in the Underworld.
Description
The deceased human consisted of two parts: the adda and the gidim. In Sumer, the body (adda) was often buried under the floor of the family home at which time the gidim separated and went down into the Underworld.
Powers
A gidim could be powerful, depending on personal valor and accomplishments of the deceased while alive and also on the number of sons he had. A gidim was weak if the deceased had few or no sons or had achieved little during his lifetime. Powerful gidim could return to the land of the living while weak gidim might not have sufficient strength to make the journey back up to the Great Above.
Behavior
The worst that could happen was for a dead person not to be buried. If that happened, the gidim, even a weak gidim, was liable to persecute whoever was responsible. Once the deceased had been properly buried, the gidim descended to the Netherworld where it stayed unless not properly fed or remembered by the living, in which case, if it was powerful enough, it returned to the Great Above to haunt those who had been negligent.