As the adventurers work to track down the missing colonists, the trail leads to a nearby island. There, the adventurers discover the submerged ruins of a cathedral dedicated to a now-dead god that has become a lair of an ichthyic monster and its cunning minions. The adventurers must fight their way through flooded chambers and vicious monsters to find the kidnapped colonists and learn the greater threat to the region and to humanity as a whole.

"The Flooded Cathedral" is a Pathfinder Roleplaying Game adventure for 7th-level characters. The adventure continues the Ruins of Azlant Adventure Path, a delve into the lost past of humanity's first empire. Several new monsters, a look into the gods of ancient Azlant, and more information about the complicated construction of clockworks round out this volume of the Pathfinder Adventure Path.

Each monthly full-color softcover Pathfinder Adventure Path volume contains an in-depth adventure scenario, stats for several new monsters, and support articles meant to give Game Masters additional material to expand their campaign. Pathfinder Adventure Path volumes use the Open Game License and work with both the Pathfinder RPG and the world's oldest fantasy RPG.