The Roshamuul Cistern is a large dungeon which acts as a reservoir for all of Roshamuul. The dungeon is infested with Terrorsleeps and Feversleeps and has three Shiversleeps which seem to manage the cistern. Most of the stairs in the cistern do not react like normal stairs, taking you to where you would not expect. However, unlike the Lower Roshamuul ramps, each staircase has a specific destination which does not change.
Several parts of the Roshamuul Quest take place here.