Incubi and Succubi. Oh, this is a fun one. Sex Demons of the Night. Bloodsucking fetish dream weavers.
According to the dictionary…
Incubus: 1: An evil spirit that lies on persons in their sleep; especially one that has sexual intercourse with women while they are sleeping.
Succubus: A demon assuming female form to have sexual intercourse with men in their sleep.
But we all know that’s not enough information.
The name succubus comes from Old Latin, and means “to lie under.” Incubus is from the Latin incubo for “nightmare.”
The two are the male and female version of the same myth. According to medieval folklore, they were demons (as in Biblical) who feasted on the life force of men/woman through dream sex. Many tales say they actually suck the life out of their dream partner. Some historians actually reference the Bible to validate their claims (Proverbs 2:18-19, Isaiah 34:14).
So, Are They Real?
There were some pretty big historical sources (St Augustine, Thomas Aquinas) that swore up and down Incubi and Succubi were real and that the demons could spawn children with humans.
Again, the Bible speaks of demons, but it never actually refers to these two in particular. Many people make many wild claims about what the demons could and couldn’t do.
Apparently, these wet dreams can turn into abusive rape scenarios pretty fast. After a while, there’s even physical manifestation and they’re not clean houseguests. Shattered furniture, torn up clothes, and broken everything seems to be the pattern.
The Modern Story
Personally, my experience with the modern version of the story is that Incubi and Succubi are a sub-class of vampire with high sexual urges. Some of them actually feed on lust and others just really, really like good sex.
But it’s your story. How will you write it?