Abyssal Depths
The Abyssal Depths are a side area accessible from Abysses in the Abyss league.
Abysses may spawn a portal to the Abyssal Depths instead of an Abyssal Trove. The Depths are a relatively large area of winding passageways that contain a high number of rare enemies as well as Hoards; both may drop Abyss items such as the Stygian Vise.
The boss, situated in a separate arena, is the Stygian Spire. This stationary totem continually summons enemies, including rares, and must be defeated in 80 seconds.