H. P. Lovecraft (with Cthulhu attacking a ship in the background)
H. P. Lovecraft is the author of the works that comprise the Cthulhu Mythos, reintroducing the world to Cthulhu. His works are all based on the prior work of Abdul Alhazred many centuries earlier, in writing the Necronomicon. While many people think H. P. Lovecraft was an author of fiction, he was actually a great prophet whose works are the gospel of the Cult of Cthulhu. His complete works can be downloaded here in a variety of formats.