Ghosts, Hags, Incubus, Succubus, etc.
...demon in male form that seeks to have sexual intercourse with sleeping women; the corresponding spirit in female form is called a succubus. In medieval Europe, union with an incubus was supposed by some to result in the birth of witches, demons, and deformed human offspring. The legendary magician Merlin was said to have been fathered by an incubus. Parallels exist in many cultures. The word incubus is derived from the Latin incubus ("nightmare") and incubare ("to lie upon, weigh upon, brood"). In modern psychological usage, the term has been applied to the type of nightmare that gives one the feeling of a heavy weight or oppression on the chest and stomach.
...in European folklore, an ugly and malicious old woman who practices witchcraft, with or without supernatural powers; hags are often said to be aligned with the devil or the dead. Sometimes appearing in the form of a beautiful woman, a succubus is a hag believed to engage in sexual intercourse with sleeping men, causing severe nightmares and leaving the victim exhausted. Although viewed in most lore as the antithesis of fertility, the hag is believed by some scholars to be a remnant of primitive nature goddesses.
Discussion of sociosexual behaviour would be incomplete without some note of the role it has played in ceremony and religion. While the major religions of today are to varying degrees antisexual, many religions have incorporated sexual behaviour into their rites and ceremonies. Human beings' ancient and continuing interest in their own fertility and in that of food plants and animals makes such a connection between sex and religion inevitable, particularly among peoples with uncertain food supplies. In most religions the deities were considered to have active sexual lives and sometimes took a sexual interest in humans. In this regard it is noteworthy that in Christianity sexual behaviour is absent in heaven and sexual proclivities are ascribed only to evil supernatural beings: Satan, devils, incubi, and succubi (spirits or demons who seek out sleeping humans for sexual intercourse).