Source: The Reaper's Right Hand, pg(s). 42
Duskfathom is the undercity of Axis, located beneath Aktun, and the divine realm of Norgorber. It consists of buildings that hang like stalactites from the ceilings of dark caverns, isolated dungeons rising from the depths, and pools of factory residue that give birth to obscene monstrosities. Divination into Duskfathom from outside is impossible, as is teleportation into or out of Duskfathom. Portals from Duskfathom lead to the upper layers of Hell, Abaddon and the Abyss, and provide a way for their denizens to raid Axis.