The PCs are now the owners of the lost city of Saventh-Yhi, right? Because as soon as they get it, the powerful Gorilla King and his simian disciples come to claim it. At the same time, the PCs learn that a missing pathfinder is imprisoned in an underground city beneath their new property. However, before they can rescue him, the PCs must venture into seven ancient vaults to find the entrance to the hidden city. Will they survive the dangers of such strange constructions, or will they succumb to madness first?