Blackmoor University did not get the soulbound technology right on the first try. Before settling on synthetics, they made many attempts to bind a soul into a “normal” material body beyond its natural bounds, most of which resulted in utter failure. The bonds were not strong enough to keep the soul from dissipating across the mortal boundary. The wizard-priests were only partially successful in calling the souls back. Some returned out of a sense of duty to the Empire. Very few, either twisted by the experimentation, or simply evil to begin with, returned bent on vengeance against the scientists, and the Empire that sponsored such abominable research.