The Writhing Chaos

The Writhing Chaos (also variously called the Abyss, the Hells, or simply Chaos) is a sprawling landscape of anguish, chaos and evil. The very ground beneath your feet is comprised of a foulness called the Writhing Mass--the collection of the lowest, weakest evil souls to dwell here, taking the shapes of squirming maggots.
The Plane of Chaos was never created intentionally, rather this land of torment was, ironically, borne of good intent. The gods had decreed a heavenly plane be created for the souls of good creatures, and so created the Court Macabre to judge who may be worthy of this new heavenly realm and allow them passage. This created too a great many evil souls which were now to be rejected, and by the The Second Rule, the gods could not truly destroy any soul permanently. And so, with every evil soul rejected from Sanctuary, this land of Chaos grew like a lake growing from rainwater. When The Red God was cast out from Sanctuary and descended into Chaos, and sculpted this lake of damned souls into a kingdom of dread.

Creation of Infernals

When a Demon Lord is in need of new servants, they pluck a soul from among the writhing mass. The soul is given new form, purpose and a semblance of freedom from their torturous existence--so long as they carry out their master's will. Infernals that succeed in their tasks or otherwise gain power continue to grow, further separating themselves from the writhing mass that once consumed them. When an Infernal is slain outside the Hells, their soul is pulled back to damnation, returning to the form of a worthless, writhing maggot.

Vrunics

For those living creatures of the material plane who have already fallen to evil, they know their fate is to squirm among the writhing mass for eternity. A rare few seek absolution, others tread further down the path of darkness and enter into an accord with an Infernal, becoming Vrunics . Vrunics are a loose collection of warlocks and servants of chaos that have traded something valuable (usually their own soul) to a demon. In exchange, upon their death the vrunic will be transformed into a lowly, lesser demon--bypassing the writhing mass altogether, at least until they are slain.