Beneath Mount Waterdeep lies the largest and deepest dungeon in the world. It sprawls out under the city, plunging miles deep. Like feelers, its caverns twist into the Underdark.

In the Age of Elves, the ancient Melairkyn Dwarves first excavated the tunnels that became their Underhalls, but their hold did not last long. For the Drow dug their own tunnels up from below, and the dwarven kingdom collapsed.

The strongholds were later claimed, altered, and expanded by the Mad Mage and his apprentices, Halaster’s Heirs — who are believed to dwell in the dungeons to this day. What drove them deep into the earth remains a mystery, but Undermountain’s allure is a siren song that still draws many.

The Mad Mage is rumored to have filled the dungeon with traps, monsters, and cursed magic most foul from across the multiverse. The only known entrance to the Undermountain is within the The Yawning Portal, an inn built upon the site of the Mad Mage’s tower ages ago.

Ways In and Out

Though the most infamous entrance to Undermountain is the Yawning Portal Entry Well, dozens of secret entrances abound, be they whispers about tunnels beneath the house of a cruel noble or the ale-spurred tavern tales spread by members of the Cellarers & Plumbers’ Guild. Control of these secret paths often changes hands, due to dangers in the deep or treachery in the ranks.
Undermountain Entrances

The Levels of Undermountain

The Upper Levels

The Upper Levels of Undermountain have always been the busiest areas—more sorts of numerous, organized beings and more adventurers, spies from the city, and organized humanoid tribes roam these levels than any others. Things left unattended for more than a day, unless secured or hidden, are rarely found undisturbed thereafter.

The Dungeon Level. The first level of Undermountain, well traveled by adventurers descending via the Entry Well. The adventurer frontier town of Downshadow can be found here.

The Arcane Chambers. The second level of Undermountain. This level is said to hold the ancient laboratories for the Mad Mage’s apprentices. This level is famous for the Goblin Market.

The Sargauth Level. The third level of Undermountain connects to Skullport by way of the River Sargauth.

The Deep Levels

The popular name for these layers of Undermountain, the Deep Levels, comes from an old poem. In truth, they are by no means the deepest levels of the dungeon, and have also
been called the Apprentice Levels, because Halaster’s apprentices have dominated (but in no sense controlled) them, building their Dooms in these halls.

Muiral’s Gauntlet Most mages in the north have heard of Muiral, one of Halaster’s Heirs. Muiral’s Gauntlet is the name given to the tenth level of Undermountain in the Professor’s Journal.

The Dark Levels

Sages refer to the many layers of Undermountain that lie between Undermountain’s Farm Level and the Seadeeps as the Dark Levels. Many of these sublevels are accessible
only through portals and have rarely been visited by adventurers who survived to tell their tales back in the city, and so they are largely mysterious even to Undermountain experts.
All of this leaves sages free to invent or ascribe any features to these sublevels as they see fit while hungering for real information.

The Gauntlet Below

This vivid term refers to the three lowest main levels of Undermountain plus the interweaving sublevels among them. This layer of the dungeon gets its collective name from the series of deadly perils faced by creatures attempting to ascend into the heart of Undermountain from deeper locations. It’s said the Mad Mage himself dwells here in the deepest dark.

Vanrakdoom – There is said to be a stronghold of great evil deep beneath the earth. From there, the Dark Army of the Night, dread followers of the evil Queen of Darkness seek to draw all of Waterdeep into darkness and death.

On the wall in the Map Room, the party found a fresco that appears to be a map of the levels of the dungeon.



City of Splendors. Dungeon of Madness. sethwhite