Succubus usually this designates the medieval Christian concept of a lascivious she-demon, which has been called a variety of names, the most common is Daughter of Lilith.
Supposedly such demons (plural Succubae) copulated with men in their dreams and sucked out the essence of their souls, or seamen. It was thought the succubus caused the man to have a nocturnal emission while dreaming of an erotic encounter with a woman, and from the emission the succubus formed a new spirit. A.G.H.
Source:
Walker, Barbara G., The Woman’s Encyclopedia of Myths and Secrets, New York, HarperCollins, 1983, p. 960