A demon spawned from, and perhaps created by the legions of Hell because of, European folklore during the medieval ages, which takes the form of an attractive female to seduce men. Its male counterpart is the Incubus . They draw energy from men to sustain themselves, often until the point of exhaustion or death of the victim.
Lilith, and her daughters, the Lilim, are considered succubi. They have supernatural abilities, largely involving seduction, including the aiblity to produce pheromones which cause feelings of almost unquenchable lust in men, and there are almost no beings in the world, male or female, which can resist the charms of a succubus. In fact, the world "succubus" is used often to describe any supernatural temptress.
They are capable of taking vessels, in their case, female humans who are either willingly or unwillingly connected with the demon, with the Demon being able to reside within and control the body of the vessel. All forms and vessels of succubi are infertile.
The natural form of a succubus is that of a very shapely woman, with large, bat-like wings or demonic features such as horns, a tail, hooves and fangs.