Succubus

In medieval legend, a succubus (plural succubi; from Latin succubare, "to lie under") is a female demon which comes to men, especially monks, in their dreams to seduce them and have sexual intercourse with them.

This legend was an explanation for the phenomena of wet dreams and sleep paralysis.

Lilith and the Lilin (Jewish), Belili (Sumerian) and Rusalka (Slavic) were succubi.

Compare: incubus.