Gatekeepers of Torghast

Each wing of Torghast has its own set of bosses: Coldheart Interstitia has Dark Aspirant Corrus (Dark Ascended Corrus) and Elder Longbranch and Decayspeaker; The Soulforges has Arch-Suppressor Laguas, Observer Zelgar, and The Grand Malleare; Cellblock Sentinel is tied to its own wing; The Upper Reaches has Goxul the Devourer, Synod, and Patrician Cromwell; Skoldus Hall has Custodian Thonar, Warden Skoldus, Writhing Soulmass, Kosarus the Fallen, and Gherus the Chained; Mort'regar has Warden of Souls and Binder Baritas; and Maw of the Maw features the Watchers of Death and Maw of the Maw itself, which appears as a blob with skeletons inside.

On Floor 3, near the Broker NPC Ve'nott, you will find a small purple hologram-like model showing the boss that awaits at the end of the run. If it is a boss you still need for the achievement, continue to Floor 6 and defeat it. If it is not the boss you need, exit Torghast and re-queue.

Queue for Twisting Corridors Layer 1 since it can pull from random Torghast wing sections, allowing you to encounter bosses from multiple wings in one session. Stealth or run past enemies to the floor's final elite, kill it, and proceed to the next floor, checking the Floor 3 hologram before committing to the full run.

Entering Layer 16 of any wing makes boss kills straightforward at max level with gear over 470 item level. Run past all enemies to the boss standing in front of the portal at the end of each floor — you can enter the portal while in combat, so focus only on killing that boss.