"If Heaven is eternal, likewise so is Hell."
-J.C. Ryle
Across the Unknown vast swathes of the temperamental, primordial plane-stuff boil over like molten lead and fester like cracked skin beneath the desert sun. The tracts of tainted earth are known collectively as the Fellands. Spoiled beyond repair and filled with the desperate screams and the echoing wails of devil, elemental and mortal soul alike, reverberate from the broken chasms and the charnel pits of the devil overlords.
These lands are where the Infernal Kingdoms boils up into the Unformed Lands. Here, the mutable landscape recoils at their existence, something about the psychic influence of powerful devils warps the land to their liking, forming terrible kingdoms for some of their most powerful devils to inhabit. Some, like Unknown, hold domain over the cracked and tortured lands where the build vast dungeons and pits to torture any who wander into their domains or those that have come to fulfill their end of a devil's bargain.
Yet, even the infinite seas of the Unshaped Lands are not outside their touch. Black abysses of shadow loom over doomed trenches beneath the oceans' wake here. Powerful fiends like Unknown stalk the nether of these infinite abysses, consuming wholesale, those that fall into their depths or those who must pay their bargains as fuel for the monsters.