Hell, which exists only as a summation of human fears and agonies, can be roughly described as alive itself.
Forever shifting and augmenting to suit the necessity of the whole, the Hellscape often blurs the lines between wildlife and scenery. This can make biological classification nearly impossible, but although its scorched environment is populated by a variety of unique demons and gouls, few are as astonishing to witness or difficult to classify as the aptly named Hellmountain.
A mobile ecosystem, this massive creature plays host to thousands of other demons that dance and laugh as they breed across its vast surface. All powered by the eternally burning flame at its top that functions like a miniature sun.
The creature above is a juvenile Hellmountain, still sprouting the large toxic tree-like growths that an adult will grow into a small forest on its thick hide. The younger specimens will spend years constantly treking until the find a suitable location to root and grow.
Although it can spend decades in a stationary position, it will seemingly at random uproot itself and stalk across the land in search of a new location to sink its tuber-like limbs deep into the rocky earth. As the Hellmountain grows older its periods of mobility gradually decrease, and its few remaining movements sharply decrease in speed and distance. Eventually the creature will "Die" or more accurately, it will simply stop moving and gradually extinguish its flame. Becoming a permanent addition to the infinite desert of splintered bone and tortured screams that makes up Hell.
Do not approach this creature, although it is often dormant, the thousands of deadly monstrosities that call its unscalable surface home never sleep, and they are always hungry.