Ruins of Undermountain II: The Deep Levels (1994) arrived after the success of the original Undermountain box set (1991). Ed Greenwood’s megadungeon was an old school throwback not often seen in the Nineties, with unbalanced encounters, countless traps and portals, and a whole lotta unkeyed locations for the DM to populate.
The original Ruins of Undermountain (RoM) featured 4 large poster maps of the dungeon’s first 3 levels, all loosely interlinked. I ran my boys through a few Undermountain sessions years ago (some short write-ups here, here, and here). The little campaign petered out for reasons I can’t remember. It really is a vast dungeon; easily being a campaign setting in itself.
RoM1 was so successful that it was reprinted in 1993 with the thicker box TSR was using at the time. RoM2 shares this later format. Both sets were still promoted as of TSR’s 1996 catalog. Three Dungeon Crawl modules set in Undermountain followed in 1996-7. (See the Waterdeep & Undermountain page at my RPG reference site)
RoM 2 is tagged as “The Deep Levels”. These are largely isolated sublevels, or between levels encounter locations, much like the later modules. Unlike the first set, most locations are keyed. This set is perfect for when the players step through a teleportation portal. Give them something new, without teleporting them out of the dungeon altogether.
The Ruins of Undermountain II: The Deep Levels [BOX SET]
1994 … Donald Bingle & Jean Rabe & Norm Ritchie … TSR 1104 … ISBN 1560768215
These out of print sets are collector items, with collector prices. If you’re just looking for a table play copy, follow the DriveThru link for a PDF and/or paperback reprint ($14 as of this writing).