From the introduction:
The Heart of the Sunken Lands is a detailed wilderness adventure module designed to be used with the Tome of Midkemia. With slight modifications it can be used with most currently available fantasy role playing games.
This Booklet Contains:
1 Information about the origins, climate, history, and inhabitants of the Sunken Lands.
2 Encounter charts detailing the creatures, plants, and objects to be found in the Sunken Lands and the relative chances of encountering them.
3 Detailed descriptions and maps of major encounter areas, including a room by room breakdown of the Ishapian temple and a section by section breakdown of the People of the Pit area.
4 Gamemaster's maps of the entire Sunken Lands at the same scale as the Player's map, showing detailed terrain features, major trails and places of interest in the Sunken Lands.