Undermountain refers to the extensive network of dungeons, catacombs, passages, tunnels, vaults and caverns that plunge deeply into the earth beneath Firetop and Firetop Mountain. Initially part of the earthworks of the Melairkyn Dwarves, it was later siezed by the powerful mage Zagor, who has remade it in his own, insane way.
Numerous levels exist, from the upper reaches of the Dungeon Level, to the noisome labyrinths of the Fungus Farms, from the deadly lanes of the Gauntlet to the lightless river caves of the Sargauth level. Some are inhabited by monsters, or by traps, or by the grim civilisations of the gloomy caverns that live below the earth – Mind Flayers, Drow, Sverfneblin, Duergar and others.
These races lived in an uneasy truce, for Halaster was never one to allow infighting within a realm he had mastered himself for an age. But since his mysterious destruction, the place is a powderkeg, ready at any moment to erupt into a huge war for domination.
Skullport is perhaps the largest and best known town in its reaches, on the Sargauth level. But other pockets of civilisation exist, some more wholesome than that den of iniquity, others far worse. Until recently, a large Drow city existed in its lower regions, sitting half-way up the huge sinkhole known as [[Belkram’s Fall]], but this has been shattered in the earthquakes that accompanied the death of The Mad Mage, and there has been an influx of displaced dark elves as a result.