Undermountain: The Lost Level, written by Steven E. Schend, was released by TSR in 1996. It is the first of three Dungeon Crawl adventures set in the largest, most dangerous dungeon in the Forgotten Realms, Undermountain. The adventure is meant for 4-8 characters, levels 7-9.
"Far be it from me to impugn the mettle of adventurers such as yourselves, but daring the depths of Undermountain merely for fortune's sake is more absurd than kicking a sleeping dragon in the nose for sport. Even so, you've returned for another trip to the Underhalls, so be prepared. You stand to enter the Lost Level this time—gird yourselves for diplomacy as well as destruction. You'll find the last stronghold of an extinct dwarven clan—do be good enough to extend the greetings of the Blackstaff to Bandaerl. There's also a dark vampiress who enjoys a good hunt, and be sure to mind the beholders—they're trained to keep you from escaping. Enjoy, and don't say Khelben didn't warn thee."This DUNGEON CRAWL adventure includes 32 pages of combat and role-playing hearkening back to classic AD&D dungeons of old. This is a stand-alone module and does not require additional support materials. It can easily be inserted into a campaign on any world, but best fits an Undermountain or Waterdeep campaign within the Realms.