Pandemonium

Pandemonium is probably the least inhabited of all the Outer Planes. And for good reason: It's arguably the least hospitable. Sure, there are hotter planes and colder ones, ones with crueler denizens, and so on, but none are any lonelier or more maddening. This birdcage's like an endless cave system, filled with winds that scream their way from one side to the other. Those cutters in the Bleak Cabal think it's a decent place to set up shop, but they're about the only ones.

Geography

Layers
Pandesmos. This first layer of Pandemonium has the largest caverns, some big enough to hold entire nations, if it weren't for the incredible winds. Nearly all its tunnels have a stream of chilly water running along a wall. In places, these streams even flow down the center of the tunnel, hanging in the air. The headwaters of the River Styx are here. Pandesmos is also the most inhabited of Pandemonium's layers, though that ain't saying much. In isolated places, a cutter can sometimes find a citadel or even a city, but mostly there's just howling wasteland.
Cocytus. The tunnels here tend to be smaller than in Pandesmos, and the wind is more piercing, too. The resulting wails cause Cocytus to earn the tag "the layer of lamentation," and they'll stretch a sod's mind past the breaking point. Strangely, the tunnels here bear the marks of having been hand-chiseled at a time so long ago that their origins are a mystery even to the powers.
Phlegethon. This layer is one of deep darkness and dripping water. The rock itself absorbs light and heat, which hampers all types of visibility. Gravity here is oriented in one direction only, which — with the dripping water — gives rise to immense stalagmite and stalactite formations.
Agathion. Rather than tunnels, Agathion consists of isolated holes within endless rock. Where portals open into these bubbles, the wind forms cyclones capable of carrying away a quarter-ton creature. Holes without a portal to another layer are Filled with utterly still, stale air or vacuum; they sometimes serve as vaults where the powers hide things away (like troublesome monsters).
SPECIAL PHYSICAL CONDITIONS. Pandemonium is made up of cavernous tunnels twisting through solid rock, and it's filled with howling winds. These tunnels range in size from mere crawlways to huge bores miles in diameter. No matter what the size, though, nearly all have two things in common: First, gravity within them is oriented toward whatever wall a cutter's nearest at the time. Second, they're filled with the eternal wailing of winds. In some cases this is little more than a breeze, carrying distant echoes that sound like the cries of beings in torment. In others it blows with supernatural force, causing a deafening caterwauling felt more in the bones than heard in the ears, making even the largest of caverns throb with its intensity. 'Course, in such gales the noise is the least of a berk's troubles. Winds that fierce can pick up a poor sod and carry him for hundreds of miles, banging his body off rock formations until there's nothing left of him.
Given the infernal noise on this plane, it shouldn't be surprising to learn that most of the poor sods here are barmy in one way or another. Oh, they may seem perfectly sane when a berk first meets them, but their madness will show when least expected.

Fauna & Flora

There are no true natives of this plane. Those beings who dwell here seldom do so by choice. Most were either banished or came here to hide and have never been able to leave. Powers here include Gorellik of the gnolls, Hruggek of the bugbears, and the Fairy Queen of Air and Darkness. Loki of the Norse pantheon keeps a hideout here as well. Finally, Zeboim (of the DRAGONLANCE saga) and Talos and Auril (of the FORGOTTEN REALMS setting) are said to live on this plane.

Natural Resources

One of the towns run by the Bleakers, known as the madhouse would be your best bet for resources. well, as best a bet you can get. See, there's always lots of stuff for sale in the Madhouse, just not always what a cutter wants. See, the Madhouse is sort of like one big caravan. Beings come from all around to trade here, but there aren't any natural resources to speak of, nor any craftsmen to make a thing to order. What's more, the market's constantly changing here. Merchants come in, decide they can't stand the noise and leave; buyers wander through with no rhyme or reason; and petitioners amble in with some unusual gem or item they found out in the tunnels, and suddenly prices go crazy as everyone clamors for the find. The result is that what's for sale and what's being sought is constantly changing, and prices vary wildly. So a cutter might come one day and find bargains galore on magical swords, but no travel rations at all, then come again a week later to find a sale on lanterns, but not a drop of oil for them.

Type

Dimensional plane