Succubae are demonic female creatures from medieval legend that enter the dreams of men and seduce them to drain their life force. The modern succubus is more direct than that, and most don't need to absorb any additional energy from men in order to survive anyway, which has actually given them something of a reputation as harmless 'eye candy' monsters. Their monster form is very close to their human form, although they possess bat-like wings and occasionally other demonic traits, such as tails, horns, razor teeth, etc. This is thought to be from the succubae's erratic mating patterns, since they frequently seduce creatures of other species.
But don't be fooled by their reputation! A succubus can be very strong, and possesses charm and illusion magic! Although not the best up-front fighter, a man who lets his guard down around one won't last long.