Mysteries of the Moonsea is an accessory for the Forgotten Realms which details the Moonsea region, a perilous frontier ruled by tyrants and threatened by monsters, with cities consumed by decadence and war and where conspiracies abound. This accessory contains 37 loosely connected adventures that can be run individually or linked to form the bases of a campaign in the Forgotten Realms. The book also presents maps and descriptions of the cities of Melvaunt, Hillsfar, Mulmaster, and Zhentil Keep, and statistics and descriptions for 15 important villains of the setting.