Sandy Petersen's Cthulhu Mythos for Pathfinder
Sandy Petersen's Cthulhu Mythos for Pathfinder - Rules of Play says:
Sandy Petersen is the undisputed authority on the Cthulhu Mythos in games as the author of the groundbreaking game Call of Cthulhu, the first game ever to bring H.P. Lovecraft’s work to the gaming world. He now proudly presents the definitive and ultimate guide to bringing Lovecraft to the high fantasy, sword and sorcery worlds played using the Pathfinder rule system.
Here, your band of heroes can now fight (and maybe even defeat) monstrous horrors and bizarre, inhumanly advanced races in adventures featuring these unique entities, their magics, and the alien technologies accurately portrayed from Lovecraftian works! This core rulebook features a bestiary with over 100 creatures, monstrosities, and Mythos Entities authoritatively revised and updated for use with Pathfinder, plus Plot Hooks and Campaign starters, information on Mythos Alien and Bizarre Technology, new expansive Insanity Rules, and details on Cults of Cthulhu and the Necronomicon and other blasphemous Tomes, as well as new Rituals, Spells, Archetypes, and Class Options.