As exciting as the surface of Ptolus can be, many adventurers find what goes on beneath the city streets to be of even greater interest. Whether it’s a section of Ghul’s Labyrinth, a natural cavern, an area of Dwarvenhearth, or some unrelated subterranean location, most of the city’s inhabitants call such places collectively “the Dungeon.” Many of the adventures in the typical Ptolus Campaign take place below the city in one of the many disparate areas covered in the following chapters.

Part IV offers a brief introduction to the areas beneath the city, focusing mainly on what is known as “Ghul’s Labyrinth”: the network of passages and chambers created long ago by the dark lord Ghul. Subsequent chapters here discuss an “unofficial” underground territory of Ptolus called the Undercity. Although these regions are not located near each other and serve very different purposes, folk lump them together in conversation for convenience sake. And it would be a mistake to overlook the city’s sewers as a significant under-realms location— both subterranean inhabitants and delvers from the surface use the sewers to get around underground. This section of the book also covers Dwarvenhearth, an ancient city so infamous that many people think it comprises the entire Dungeon. Sealed for many centuries, these dwarven halls teem with great treasures as well as guardians and traps. The same can be said for much of the Caverns, an extensive network of natural passages and caves running below the city of Ptolus. These Caverns hold many dread secrets, from the fortresses of the dark elves to the ancient demesne of the Galchutt’s servants.

Players should not read these chapters. The information found in Part IV is best left for the player characters to discover first hand.

Chapter 19: What’s Down There?
Chapter 20: The Undercity
Chapter 21: The Sewers
Chapter 22: The Caverns
Chapter 23: Dwarvenhearth