Noisome Vale was once ruled by a powerful balor called Tarnhem, though he has gone missing. The layer's atmosphere is a haze of acidic gas constantly regenerated by volcanic vents that scar an utterly blasted landscape. A ravine cuts through the landscape of the Noisome Vale, but it is not filled with water or even condensed acid. Instead, it channels a flood of slick, writhing worms that vary in length between 1 inch and 10 feet. These worms inhale the sulfur fumes endemic to the layer and exhale breathable air. The worms' respiration affects both shores of the river to a distance of 50 feet on either side, effectively scrubbing the air free of sulfur gas.

Tarnhem's manor is built along the ravine. Thanks to the worms, it possesses a breathable atmosphere, though the constant susurrus of the writhing worms below is maddening. Tarnhem's demonic staff still maintains the manor despite the absence of Tarnhem himself (the staff believes he is imprisoned offplane). Despite Tarnhem's disappearance, the demons that guard the manor still take a dim view of unannounced visitors.