“The Great Old Ones are a loose pantheon of ancient, powerful deities from space who once ruled the Earth and who have since fallen into a deathlike sleep. H. P. Lovecraft named several of these deities, including Cthulhu, Ghatanothoa, and Yig. The majority of these have physical forms that the human mind is incapable of processing; simply seeing them renders the viewer incurably insane. Although worshipped by deranged human (and inhuman) cults, these beings are generally imprisoned or restricted in their ability to interact with most people (beneath the sea, inside the Earth, in other dimensions, and so on), at least until the hapless protagonist is unwittingly exposed to them. Lovecraft visited this premise in many of his stories, notably his 1928 short story, "The Call of Cthulhu", with reference to the eponymous creature. However, it was August Derleth who applied the notion to all of the Great Old Ones.”Source
Below is a list of all Great Old Ones gods currently available.