Onyx the Invincible and the bumbling Tertius comb the sewers and cavernous underdark of the City of Splendors in search of their missing friend. Meanwhile, Timoth finds himself at the mercy of a malevolent Mind Flayer, a sinister Drow, and their even deadlier master - Xanathar the Beholder, Crime Lord of Waterdeep! Plus, hear the tale of how a dwarf thief and stalwart centaur once crossed swords then became the best of friends.