Undermountain

Undermountain is a vast dungeon crawl under the area of Waterdeep in the fictional world of the Forgotten Realms campaign setting for the Dungeons & Dragons fantasy role-playing game. This dungeon has been used as an adventure setting for several computer games.

Creative origins
Undermountain was created by Ed Greenwood in 1975. It was the first dungeon for his fledgling Forgotten Realms campaign setting, and he used the Undermountain in both his Dungeons & Dragons and Advanced Dungeons & Dragons games.

Shannon Appelcline, the author of Designers & Dragons, wrote, "Readers of Dragon magazine saw their first hint of Undermountain in Dragon #106 (February 1986), where Ed Greenwood led off an article called 'Open Them If you Dare'. [...] However, unbeknownst to them, Dragon readers had been reading material associated with Undermountain for years. Some of the spells and books in Greenwood's 'Pages from the Mages' series, which began in Dragon #62 (June 1982), and the 'Rogue Stones and Gemjumping' magic from Dragon #116 (December 1986) were 'first inflicted' on PCs in Undermountain. [...] Rather surprisingly, there's no explicit mention of Undermountain in the Forgotten Realms Campaign Set (1987). However, 'The Halls of the Beast-Tamers' adventure is of some note. The portal described in area 11 was intended to send players to 'the uppermost main level of Undermountain', at least according to Ed Greenwood's home campaign. [...] The first notable mention of Undermountain in print was in FR1: 'Waterdeep and the North' (1987)".

Description
Undermountain? Ah, yes. A great place to have fun, the most famous battlefield in which to earn a reputation as a veteran adventurer – and the largest known mass grave in Faerûn today.

– Elminster of Shadowdale The published campaign information originally described Undermountain as at least nine levels deep and possibly deeper. The majority of Undermountain was created and expanded from the natural caverns already in the area by a powerful and ancient wizard named Halaster Blackcloak, who dwelt in Undermountain and uses it as his personal playground and laboratory (307 DR – 1490s DR). The most well-known entrance in the Yawning Portal on Rainrun Street in the upper part of the Dock Ward. Durnan the barkeeper and owner of the tavern charges 1 gold per adventurer to enter Undermountain from the well in the center of the taproom.

The third level contains Skullport, also known as the Port of Shadows, and Qilué's Promenade of Eilistraee, a temple complex northeast of Skullport dedicated to the good-aligned followers of Eilistraee.

There are ruins of an ancient Ghaunadaur-worshiping drow city in a part of Undermountain near the Promenade whose inhabitants were single-handedly driven away by Halaster while he was creating Undermountain. The lower three levels were delved by dwarves. Madgoth's Castle also lies below the depths of Undermountain. Below that not much campaign information was originally available. 2018's Waterdeep: Dungeon of the Mad Mage describes Undermountain as 23 levels deep and contains a chapter on each level.

Many magical portals lead into Undermountain from all over Faerûn.

It was later established that "Undermountain was created because Halaster was compelled by his own madness to build it, and to continue building it out into eternity. The Mad Mage built his original tower upon the land that would become Waterdeep by an unknown and powerful source of magic. This source was a knot in the Weave of Magic inadvertently created by an ancient elven civilization that sought to transcend reality. Halaster is more than the dungeon’s creator; he is its avatar. Halaster has died countless times, but he always returns before long. It is said that Undermountain cannot exist without Halaster, and his return is necessary to keep the dungeon from being utterly destroyed."

Jason Wilson, for VentureBeat on the topic of megadungeons, wrote that Undermountain "might even be deeper than Castle Greyhawk" and that Halaster Blackcloak is "known as the Mad Mage, and as he dug deeper under the Realms’ City of Splendors, Waterdeep, Undermountain didn’t just grow. He connected it to many parts of the Realms and the multiverse with a host of portals. As he descended into madness, he dug deeper, and his halls expanded. His apprentices, some bearing similar broken minds, added levels of their own. And others even founded a city, Skullport, which serves as not only a link to the Underdark but also the seedier side of Waterdeep. Without Halaster, Undermountain unravels, its portals going crazy and sending monsters into the city above. It creates problems for the rest of the world. So if Castle Greyhawk was a trap for the gods, then one could see Undermountain as a containment system for a mad archmage…and the terrors of the dungeon itself. It’s a trap and a prison, as much as Castle Greyhawk is for the gods."

Appearances
Appelcline also wrote that "the AD&D 2e version of the dungeon was the most extensive, with six different supplements revealing considerably spans of the dungeon, level by level. The Ruins of Undermountain (1991) detailed the first two levels, Ruins of Undermountain II (1994) described two Deep Levels and a sub-level, then Undermountain: The Lost Level (1996), "Undermountain: Maddgoth's Castle" (1996), "Undermountain: Stardock" (1996), and Skullport (1999) revealed smaller scale locales. The D&D 3e version of the dungeon instead tried to cover everything in one big book: Expedition to Undermountain (2007). It overviewed the whole dungeon, then detailed some very specific places. In its third roleplaying incarnation as Halls of Undermountain (2012), the 4e designers took a different tack. The 96-page book isn't really a sourcebook like its predecessors; instead it's a set of three loosely linked adventures that use Undermountain as a setting — and in the process tell a larger story. Halls was actually the second appearance of Undermountain during the 4e era. However the Encounters adventure, 'Halaster’s Lost Apprentice' (2010), was still unknown to most players — and had only featured the dungeon in the form of some very constrained encounters." In 5th Edition, Undermountain was revisited in Waterdeep: Dungeon of the Mad Mage.

Other media
Undermountain is the titular location of Descent to Undermountain, a game maligned as "a classic example of a game that was shipped too early." It also appeared in the novel Escape from Undermountain (1996) by Mark Anthony.

In 2003, Waterdeep and Undermountain served as part of the setting for the Neverwinter Nights computer role playing game expansion, Neverwinter Nights: Hordes of the Underdark, appearing in the first levels of the game.

The largest expansion to the free-to-play massively multiplayer online role-playing game Neverwinter was called Neverwinter: Undermountain and it launched in March 2019 for PC and in June 2019 for PS4 and Xbox One. This expansion increased the level cap to 80, added the Undermountain Campaign with five new adventure zones, and included "Halaster Encounters" where "the Mad Mage himself will make unpredictable appearances throughout Undermountain, presenting opportunities to match wit and force. Some encounters will be a challenge, while others may be more bizarre." In July 2019, it was announced that the 17th module of the game called "Uprising" would take players further into Undermountain. The premise is that "the conflict between the Illithid and the Gith erupts within the caverns of Undermountain, offering players the unique opportunity to challenge Halaster Blackcloak in an endgame, 10-player trail when he emerges to deal with these threats to his realm."