http://paizo.com/products/btpy9rbt?Sandy-Petersens-Cthulhu-Mythos

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.
Content Includes:

• A bestiary with over 100 entries, almost half never before seen in a Pathfinder book before.
• Over 25 Mythos Entities: Creatures in the Paizo's Pathfinder Bestiaries now authoritatively revised & updated in this book. Additionally, the original entries as found in the Bestiaries are also included for easy reference and comparison.
• Over 50 NEW Mythos Entries: Creatures from the Cthulhu Mythos that have never before been published in any Pathfinder Bestiary.
• Over 40 ‘Unusual Suspects': Creatures that could (and maybe should) be in the Cthulhu Mythos, found in the pages of the current Pathfinder Bestiaries. Some have been updated to reflect our new rules.
• Adventures: Plot Hooks and Campaign starters by Sandy Petersen and others.
• How to run horror in a heroic sword and sorcery setting by Sandy Petersen.
• Mythos Alien and Bizarre Technology
• New Expansive Insanity Rules
• The Necronomicon and other Tomes
• New Rituals and Spells
• Archetypes and Class Options for Base Classes
• Cults of Cthulhu and Other Great Old Ones
• Mythos Magic Items and Artifacts
• Aklo Language Essay
• Mythos Ghouls as Player Characters
• Mythos Eidolons, Familiars and Animal Companions
• Tcho-Tchos
• Gnorri as Player Characters
• Advanced Adversaries
• Zoogs as Player Characters
• Mythos Cats and Mythos Cats as Player Characters