August William Derleth (1909–1971) of Sauk City, Wisconsin, corresponded with Lovecraft from his teens. After Lovecraft's death in 1937 he co-founded Arkham House with Donald Wandrei specifically to publish his work and rescue it from obscurity, an act of literary preservation with few parallels.
Derleth coined the label "Cthulhu Mythos" and systematised the Great Old Ones into an elemental hierarchy opposed by Elder Gods — a good-vs-evil schema absent from Lovecraft's own amoral cosmicism. Purists debate whether his additions clarify or distort the original vision.