From the publisher's website:
When an unlucky historian in Absalom uncovers an infernal book from distant Tian Xia, he unwittingly unleashes a terrible evil into the city—the legions of devils imprisoned within its dusty pages. Only the book's holy counterpart can end the threat, and the Pathfinder Society has been called in to assist. Can the PCs locate and retrieve the key to ending the diabolical invasion of the City at the Center of the World, or will Absalom be drowned in the sea of destruction wrought by the Infernal Incantation?
A Pathfinder Society Scenario designed for Levels 3–7.
This scenario is designed for play in Pathfinder Society Organized Play, but can easily be adapted for use with any world. This scenario is compliant with the Open Game License (OGL) and is suitable for use with the Pathfinder Roleplaying Game.