Succubus

A Succubus is a demon in female form, that appears in dreams and takes the form of a woman in order to seduce men, usually through sexual activity. The male counterpart is known as an Incubus. Repeated sexual activity with a Succubus may result in the deterioration of health and mental state, or even death. Offspring between a Human and a Succubus is known as a Cambion.

Etymology
Succubus is derived from Late Latin "succuba", meaning "paramour"; from "succubare", meaning "to lie beneath", derived from "sub", meaning "under", and "cubare", meaning "to lie in bed".