Pandesmos

Pandesmos is the topmost layer of the Outer Plane of Pandemonium.

Geography

Pandesmos is the most hospitable layer of the plane. The caverns are the largest here, some literally thousands of miles across. Immigrants to Pandemonium tend to live on the surfaces of these massive caverns, which contained both cities and citadels, though these were very rare. Most caverns are abandoned to anything but wind. Despite the size of the caverns, they are as loud and windy as the rest of the greater plane, though the velocity of those winds is slightly less. Entire nations could fill the cavern walls, but the strong winds prevented this from ever happening.
The Styx begins here, fed by countless cold streams flowing along the walls of the otherwise rocky, subterranean wastes. Some of the streams even float through the open space in the centers of the caverns.
Dead-end tunnels with unusually strong winds (even for Pandemonium) often signal that one is at a barrier and about to pass to the lower layer of Cocytus. Flat, square portals found in Pandesmos led to Limbo and the first layer of the Abyss. Yellow squares lead to Limbo and red squares to the Abyss. The portals are inconsistent, however, and sometimes sent travelers to the wrong planes.
To reach Pandesmos with the plane shift spell required an iron planar fork tuned to the note of C♯

Type

Planar Sphere/Grouping