H. P. Lovecraft wrote “The Call of Cthulhu” in 1926, initiating the Cthulhu Mythos, one of the most widely imitated shared-world universes in weird fiction. Even in his lifetime, many other writers added to the Mythos, and after his death hundreds if not thousands of authors of weird, fantasy, and science fiction have added their distinctive elaborations on Lovecraft’s basic themes and ideas.