Treasures and secrets abound, but tread with care!

In the city of Waterdeep rests a tavern called the Yawning Portal, named after the gaping pit in its common room. At the bottom of this crumbling shaft is a labyrinthine dungeon shunned by all but the most daring adventurers. Known as Undermountain, this dungeon is the domain of the mad wizard Halaster Blackcloak. Long has the Mad Mage dwelt in these forlorn depths, seeding his lair with monsters, traps, and mysteries-to what end is a constant source of speculation and concern.

This adventure picks up where Waterdeep: Dragon Heist leaves off, taking characters of 5th level or higher all the way to 20th level should they explore the entirety of Halaster’s home. Twenty-three levels of Undermountain are detailed herein, along with the subterranean refuge of Skullport.

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Explore the Mega-Dungeon of Undermountain

The Greatest Dungeon of Them All

Dungeon of the Mad Mage is the dungeon crawl to end all dungeon crawls.

Hack, slash, connive, and conspire your way through 23 levels of Undermountain: the world-sized underground lair of Halastar Blackcloak, the Mad Mage.

23 Levels, 23 Adventure Settings

Each of Undermountain’s 23 levels is an adventure setting of its own.

Gather your adventurers and start your journey to explore Wyllowwood, a massive underground forest filled with woodland beings and werebats; or Arcane Chambers, inhabited by competing factions of goblins, wererats, and members of the Xanathar guild.

The Ultimate Dungeon, at a Glance

Undermountain teems with challenges. But navigating the book isn't one of them.

Inside, Dungeon Masters will find everything they need to make dungeon delving a breeze, including easy-to-read maps for each level and an iconographic dungeon key.