Pathfinder Adventure Path: Lord of the Black Sands (Extinction Curse 5 of 6) - Rules of Play says:

“Lord of the Black Sands” is a Pathfinder adventure for four 15th-level characters. This adventure continues the Extinction Curse Adventure Path, a six-part, monthly campaign in which the heroes lead a traveling circus as they unravel a plot to eradicate all life from the islands of the Inner Sea. This volume also includes a gazetteer of the ominous city of Shraen, new monsters, and new rules.