Fires of the Haunted City

From the back of the book:

The Scarlet Triad—slavers at the center of a vast conspiracy—have been tracked to the Five Kings Mountains. There, in the subterranean city of Saggorak, the slavers have forged an alliance with a terrifying dragon. To stop them, the heroes must navigate a complex political landscape and perhaps make an alliance of their own with a dwarven king who’s been dead for thousands of years! The Age of Ashes Adventure Path continues with “Fires of the Haunted City,” a complete adventure for 12th- to 14th-level characters.