Malbolge
The sixth layer of the Nine Hells is an endless rocky slope. Cascades of boulders are frequent, pulping anything in their path. Above, the sky boils with leprous colors. The devils on this layer take shelter in copper-clad fortresses, designed to channel and deflect the frequent rock-flows. However, nothing can withstand the worst of the avalanches. The rocky slopes of Malbolge are like Gehenna's, and a Climb check is required to move around on Malbolge's surface. See Falling on Gehenna, earlier in this chapter, for a list of Climb DCs and the consequences of failure. Maggoth Thyg: Rumors describe ancient places built underneath the slopes of Malbolge. Below the hellish rock and stone, creatures older than the devils themselves—the ancient baatorians—might still roam. A certain hard-to-find defile leads to a cavern whose walls glow with a brain-numbing, grayish light. Boulder falls often clog the defile, but somehow the cavern is reopened time and again. Devils sent by the Lord of the Sixth to investigate have never returned. Terrible cries sometimes issue forth from the cavern, echoing across Malbolge's slopes. Strangely, petitioners on this level cannot hear the cries. But devils can, and the sound is innately terrifying to them.