The Necronomicon tied directly into this mythos, since it was said to contain a lengthy account of the extra-terrestrial Old Ones, and to merely look upon its pages would be enough to inspire madness.
This Cthulhu Mythos, as it later became known, suggested that ancient, god-like beings once ruled the Earth, and could return to either destroy us or drive us all insane by anyone foolish enough to reawaken them. Lovecraft was apparently unhappy with The Hound, but both it and The Nameless City, published in 1921, marked the beginning of the author’s endeavours to set his stories in one coherent universe. The tale told of two grave robbers doomed by their theft of a jade amulet, which they recognised as ” the thing hinted of in the forbidden Necronomicon of the mad Arab Abdul Alhazred.” Although inspired by real texts, such as the Egyptian Book of the Dead, the Necronomicon was a product of Lovecraft’s fertile imagination, and mention of it first appeared in the short story The Hound, first published in 1924.
Actually, the Necronomicon has a much shorter history than its true creator HP Lovecraft had his readers believe.