Pandemonium

Pandemonium was the dismal seventh layer of the Nine Hells, Outer Planes suffused with negative energy. It was a plane of incomprehensible madness, and the only one of the Nine Hells that was inherently chaotic evil in alignment. Endless tunnels wormed their way through the blackened granite of Pandemonium, maze-like and haphazard. Open spaces were filled with howling screams, and winds strong enough to carry creatures down tunnels, forever lost.

One did not need to eat, drink, or sleep to survive in Pandemonium. However, the sensations of hunger, thirst, and fatigue would persist, and eventually become overwhelming feelings: starvation, dehydration, and madness.

Dreams could not reach a person in Pandemonium, meaning a person could not achieve REM sleep. This prevention of deep sleep caused irritability and eventually incipient madness resulting from a lack of effective rest.