The Mask of Cthulhu

The Cthulhu Mythos is a mythopoeia and a shared fictional universe, originating in the works of American horror writer H. P. Lovecraft. The term was coined by August Derleth, a contemporary correspondent and protégé of Lovecraft, to identify the settings, tropes, and lore that were employed by Lovecraft and his literary successors. The name "Cthulhu" derives from the central creature in Lovecraft's seminal short story "The Call of Cthulhu", first published in the pulp magazine Weird Tales in 1928.
Richard L. Tierney, a writer who also wrote Mythos tales, later applied the term "Derleth Mythos" to distinguish Lovecraft's works from Derleth's later stories, which modify key tenets of the Mythos. Authors of Lovecraftian horror in particular frequently use elements of the Cthulhu Mythos.