A succubus is a demon in female form or supernatural entity in folklore (traced back to medieval legend) that appears in dreams and takes the form of a woman in order to seduce men, usually through sexual activity. The male counterpart is the incubus.
According to Zohar and the Alphabet of Ben Sira, Lilith was Adam's first wife, who later became a succubus. She left Adam and refused to return to the Garden of Eden after she mated with archangel Samael. In Zoharistic Kabbalah, there were four succubi who mated with the archangel Samael. There were four original queens of the demons: Lilith, Eisheth, Agrat bat Mahlat, and Naamah. A succubus may take a form of a beautiful young girl but closer inspection may reveal deformities of her body, such as bird-like claws or serpentine tails. Folklore also describes the act of sexually penetrating a succubus as akin to entering a cavern of ice.
The word incubus is derived from Late Latin incubo (a nightmare induced by such a demon); from incub(āre) (to lie upon). One of the earliest mentions of an incubus comes from Mesopotamia on the Sumerian King List, ca. 2400 BC, where the hero Gilgamesh's father is listed as Lilu. It is said that Lilu disturbs and seduces women in their sleep, while Lilitu, a female demon, appears to men in their erotic dreams. Two other corresponding demons appear as well: Ardat lili, who visits men by night and begets ghostly children from them, and Irdu lili, who is known as a male counterpart to Ardat lili and visits women by night and begets from them. These demons were originally storm demons, but they eventually became regarded as night demons because of mistaken etymology. Written later but described as happening before the Sumerian King List was completed is the mention of the Nephilim: Christian tradition attributes the completion of the Biblical book of Genesis to the 5th century BC.