Madness is the only way out The Underdark is a subterranean realm of wonders; a vast, twisting labyrinth where fear alone reigns, home to terrifying monsters that have never seen the light of the sun. Here the dark elf Gromph Baenre, archmagus of Menzoberranzan, has cast a dark spell that ignites the magical energy of the Underdark and thereby creates a portal into the demon realm of the Abyss. However, he did not expect what emerges from the portal, and from this point on the madness of the Underdark increases immeasurably and even begins to shake the foundations of the Forgotten Realms. End this madness before it consumes you! A Dungeons & Dragons adventure for adventurers levels 1-15. For use with the Fifth Edition Player's Handbook, the Monster Manual, and the Dungeon Master's Guide.