Level 3 is the dark route that many of the slavers use to enter and leave the Well without being seen. The river exit off map was created to be used in any campaign/module where needed. This level is fairly limited, but has a few surprises. The secret hall leads to a storage facility, that also doubles as a gate region for quick traveling, and perhaps for royalty.
Years later, I adapted this dungeon into "D1-D3", and made the slavers
Drow. This was a perfect jumping off point for excursions to the