The King of Demons is named Asmodeus (Ashmedai). According to the Kabbalah, Asmodeus is a cambion, born as the result of a union between King David, and the Queen of Demons named Agrat Bat Mahlat who was a succubus.
David was the second king of the United Kingdom of Israel and Judah, and also an ancestor of Jesus. Agrat Bat Mahlat was a female demon who is referred to as succubus, and who 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.