Rivers

Underdark rivers tend to be swift, violent, and tortuous in their windings. It is a rare river indeed that flows level and smooth for more than a few miles at a time before disappearing into a deep gorge or sinkhole in a fuming waterfall. Rivers are the great builders of the Underdark, the natural force that sculpts great caverns and brings life-giving energy and food to sustain the Underdark ecology. Most rivers are surrounded by a halo of living caves, which can be valuable real estate indeed.