Rage against Creation
The Underneath is the home plane of the Demon Prince Iszitst. It is marked by a complete lack of light, and an infinite plateau that seems to stretch on forever. The ability to see in magical darkness will provide little more insight than that the floor is, in fact, black marble.
Sometimes the terribly buzzing of thousands of flies can be heard here as Iszitst approaches. When his terrible form manifests in the darkness, the sound of the insects stop, as if all falling dead at once.
Redrick breifly thought he was here when his mind was being played with by Norgorbers Creepy House