This is a list of fictional creatures from the Cthulhu mythos of American writer H. P. Lovecraft and his collaborators. Byakhee The byakhees or byakhee birds first appeared in Lovecraft's short story "The Festival" and were later featured in August Derleth's tale "The House on Curwen Street." They are the servants of the Great Old One Hastur. Lovecraft provides a description of the byakhees in The Festival: Deep Ones The Deep Ones first appeared in Lovecraft's novella The Shadow Over Innsmouth (1931), but were already hinted at in the early short story "Dagon". The Deep Ones are a race of intelligent ocean-dwelling creatures, approximately human-shaped but with a fishy appearance. They regularly mate with humans along the coast, creating societies of hybrids. Numerous Mythos elements are associated with the Deep Ones, including the legendary town of Innsmouth, the undersea city of Y'ha-nthlei, the Esoteric Order of Dagon, and the beings known as Father Dagon and Mother Hydra. After their debut in Lovecraft's tale, the sea-dwelling creatures resurfaced in the works of other authors, especially August Derleth. Lovecraft provides a description of the Deep Ones in The Shadow Over Innsmouth: Lovecraft describes the Deep Ones as a race of undersea-dwelling humanoids whose preferred habitat is deep in the ocean (hence their name). However, despite being primarily marine creatures, they can come to the surface and can survive on land for extended periods of time. All Deep Ones are immortal; none die except by accident or violence, and they can grow to massive size. They are said to serve the beings known as Father Dagon and Mother Hydra, as well as Cthulhu. They are opposed by mysterious beings known as the Old Gods, whose powerful magic can keep them in check. This detail is one of the vestigial hints that August Derleth developed as the mostly unnamed Elder Gods. Deep One hybrid The backstory of The Shadow over Innsmouth involves a bargain between Deep Ones and humans, in which the aquatic species provides plentiful fishing and gold in the form of strangely formed jewelry. In return, the land-dwellers give human sacrifices and a promise of "mixing"—the mating of humans with Deep Ones. Although the Deep One hybrid offspring are born with the appearance of a normal human being, the individual will eventually transform into a Deep One, gaining immortality—by default—only when the transformation is complete. The transformation usually occurs when the individual