Utukku

The Utukku are spirits from Babylonian and Assyrian legends. They are formed when someone is murdered, and they cannot rest until they kill their murderers, or otherwise get vengeance. Some simply return from the grave of pure malicious intent and desire to feed on the living. They can be called forth with black magic or curses. They track down their killer and murder any human they encounter on the way. It’s thought they become stronger every time they kill and grow in their desire for power, sometimes choosing to remain on earth after finding their killer. They often take the form of a man or an animal.

Citations:

Maberry, Jonathan. Vampire Universe: The Dark World of Supernatural Beings That Haunt Us, Hunt Us, and Hunger for Us. United States, Kensington Publishing Corporation, 2006.