In Geoffrey of Monmouth's History of the Kings of Britain, King Vortigern attempts three times to construct a castle to protect himself from his enemies, and thrice he fails. King Vortigern asks his astronomers and wise men how he can successfully construct the building. They advise him to seek out "a child born without a father, put him to death, and sprinkle with his blood the ground on which the citadel is to be built." Therefore, King Vortigern sends forth his men, who find the boy with no father. The boy's name is Merlin, and he has no human father, for his father was an incubus.