Acheron

From Manual of the Planes (3e):

It is where ignorant armies clash by night.

It is the refuse-plane of a million failed rebellions.

It is a plane of enforced order, where conformity is more important than good.

The hue and cry of battle is the first sound a soldier hears when arriving on Acheron and the last sound a refugee hears when leaving. That's all there is on Acheron: conflict, war, strife, and struggle. Many armies populate Acheron, but leaders are scarce. Truly, rebels without a cause are common on Acheron, whether they're petitioners, mortals, fiends, or celestials.

Acheron has four layers, each made of island- or even continent-sized iron cubes floating in an airy void. Sometimes these "Acheronian Cubes" collide, and echoes of past collisions linger throughout the plane, mingling with the ring of sword on sword as armies clash across the faces of the cubes.

Acheron hosts many deities, including Wee Jas, the deity of death and magic; Gruumsh, the god of orcs; Maglubiyet, the goblin deity; and Hextor, the deity of tyranny and self-proclaimed champion of evil.

The cubes that make up each of the four layers of Acheron are pitted and scarred with cracks and dents from their many collisions and craters from their many battles. On the orderly plane of Acheron, the cubes always rust or fracture along straight lines and at right angles. Some of the cubes are only a few hundred feet on a side, but others are big enough for whole cities and kingdoms. Geometric shapes other than cubes exist, though they are rare (except on Tintibulus, the third layer).

Vision is normal on Acheron. The plane is lighted by a gray, fluctuating illumination that varies slightly between bright moonlight and a dark, cloudy day. Hearing is also normal, though the echo of colliding cubes and the ring of battle is always in the background.