Undermountain: Stardock, written by Steven E. Schend, was released by TSR, Inc. in 1996. It is the last of three Dungeon Crawl adventures to be set in the largest, most dangerous dungeon in the Forgotten Realms: Undermountain. The adventure is meant for 4-6 characters, levels 10-14.
This DUNGEON CRAWL adventure returns once more to the hallowed halls of Undermountain, but it's a different day. At dawn of Highharvestide 1369, every practitioner of magic on the Sword Coast knew there was a problem. By midmorning, the Lords of Waterdeep confirmed the ill omens: Some brave souls worthy of the title "Hero" must enter Undermountain on a mission to save Halaster Blackcloak! Could these heroes be your group of player characters?This is a stand-alone module and does not require extra support materials. It can be placed into a campaign on any AD&D world, but best fits and impacts a FORGOTTEN REALMS campaign set in Undermountain or Waterdeep.
This source book is now available as a free PDF from WotC's website.