The Incubus and Succubus are mythological creatures that perform acts of evil by having sex with their victims. Many people believe that Incubus and Succubus are interchangeable words however they are not. The Incubus is the male version of the demon and the Succubus is the female version of the demon.
In myths incubi impregnate women with its demon seed, while the succubus impregnates itself with human seed. In some myths it is said the in order for a succubus to become an incubus it must first impregnate itself with human seed, then it can impregnate a women later.