Halaster Blackcloak, an eminent demented magician, took up residence in a dungeon he named "Undermountain".
 Hostile, labyrintic, full of mystery, his den is populated by monsters obeying him to the finger and the eye ...
 But why go into exile alone in a dungeon, and above all, why protect it?
 Our heroes will have to find out by going to the tavern of the Yawning Portal, inside which a pit leads to the entrance of Undermountain.
 This adventure progresses players from level 5 to level 20.