The heroes track down the cult of the Forgotten Pharaoh to its secret headquarters inside a giant sphinx statue in the Osirian desert, facing scorpion-men mercenaries and Areshkagal-worshiping maftets before a final confrontation with masked cultists and their leader, the Forgotten Pharaoh, who has been possessed by a fragment of Hakotep I's soul! Continuing the Mummy's Mask Adventure Path, Secrets of the Sphinx is a Pathfinder Roleplaying Game adventure for 10th-level characters. A selection of new monsters, two additional desert locales to expand the Mummy's Mask campaign, details on the ancient curses of Osirion, and the next installment of the Pathfinder's Journal written by Amber E. Scott round out this volume of the Pathfinder Adventure Path.