For Depths of Despair, you specifically need to kill the Troglodyte Chieftain Sslysk
PREPARATION: The usual start off point is "Depths of Despair". The Silk road Gold quest entrance is just next to the Hammersmith's Inn.
The quest is bestowed by Neville Storm-hammer. He's at the back of the inn having drinks with a human (Keane d'Deneith), a Halfling (Scholes of Vedykar), and an Elf (Giggs Elorreathi). They are the quest givers for all 4 Depths quests, Might as well talk to everyone if you intend to do all the quests.
All of the depths quests will require you clean up the tunnels of creatures that lurk inside. For Depths of Despair, you specifically need to kill the Troglodyte Chieftain Sslysk.
The tunnel is heavily infested by various creatures so you might have to switch weapons at every encounter. You will encounter the following:
With that cast of characters, you will need to bring in cold and piercing weapons for the spiders; muck-banes for the oozes; blunt or pure good weapons for the undead; reptilian banes for the Trogs; Axiomatic for hellhounds; and decent slashing weapons for the Minotaur’s.
If you have casters in the group, spells such as Magic Missile and Scorching Ray will be very useful. The Shaman can cast a mean Melf Acid Arrow.
Moving further west will lead you to Hell Hounds. Before the path bends to the left, you will encounter skeletons. As you head south, you will find a locked gate with a Minotaur inside.