Welcome to the Underworld Expansion of the Marmoreal Tomb Campaign Starter. This work is part of a trio of volumes starting with the Marmoreal Tomb Game Module, also dubbed “core module”, which presents a complete adventure site, the ruins of Grunn Galeb, a colony of dwarves in a region of the Eurth called the Bitter Peaks. It presents the Viper Head Pass and Erydian Vale around it, as well as the underground levels under the abandoned settlement, the Burial Vaults and Crypts of the Stone Giants of Aktum. The second volume of this trio is the Wilderness expansion to the Marmoreal Tomb, which describes the world region around the Marmoreal tomb, including the Lower Midlands and Viscountcy of Poy, includes a fully detailed village, an inn and tavern, as well as templates and game aids to help run games of explorations of the wilderness around the dungeon, and within the world of the Duinnsmere and the Eurth. The third volume you now hold in your hands.