In medieval legend, a succubus (plural succubi from the Latin succubare meaning to lay under) is a female demon which comes to men in their dreams to seduce them for their energy. As the succubus draws energy from men, the men die and she is rejuvenated.
Succubi are creatures that take the form of beautiful women in order to feed off their victims' energy.
In Elizabethville, Ohio, Dean is surprised to find an old hunter friend, Richie, working the same case. When Sam asks Dean and Richie how they know each other, Richie says to Dean, "it was that succubus in Canarsie, right?" He reminisces about the "rack" on her and how tragic it was he had to gank her, though Dean disputes that Richie was the one that made the kill.
Succubus in Lore
A succubus is a type of demonic entity that seduces men in their sleep through sexual activity. Repeated visits from a succubus are said to lead to a deterioration in health and mental well being, and ultimately death
Lilith was believed to have become a succubus after leaving the Garden of Eden and mating with the archangel Samael.