Hastur is one of the many eldritch gods of H.P. Lovecraft'sCthulhu Mythos. One of the Great Old Ones, he's known as "The Unspeakable One" or "He Who Is Not To Be Named." One of his avatars is known as The King in Yellow. For theHaiyore! Nyaruko-sancharacter, seeHastur (Nyaruko-san).