Hastur (The Unspeakable One, Him Who Is Not to be Named'", One, spawn of Yog-Sothoth, the half-brother of Cthulhu, and theoretically the. Hastur is an entity of the Cthulhu Mythos. Hastur first appeared in Ambrose Bierce's short story Derleth also developed Hastur into a Great Old One, spawn of Yog-Sothoth, the half-brother of Cthulhu, and possibly the Magnum. Is defined as a Great Old One, spawn of Yog-Sothoth, the half-brother of Cthulhu, and possibly the Magnum Innominandum (AWD). In this incarnation, Hastur. Kthanid is an Elder God and said to be the brother of Cthulhu. A member of Cthulhu's race, he helped banish his brother and the other Great Old Ones to Earth before binding them. He is the leader of the Elder Gods who live on the planet Elysia. erudition will understand me when I link them with Hastur and the Yellow Sign) devoted to the purpose Here we find that Hastur is the half-brother of Cthulhu. A Great Old One who is at odds with Cthulhu, his half-brother. One form he takes is that of a humanoid dressed in yellow garments. No relationship between Cthulhu and Hastur was mentioned in any of he did introduce him into the mythos as Cthulhu's half-brother and. Cthulhu is a fictional cosmic entity created by writer H. P. Lovecraft and first introduced in the . and was engaged in an age-old arch-rivalry with a designated air elemental, Hastur the Unspeakable, described as Cthulhu's "half- brother"