The Para-Elemental plane of Ooze is a universe of muds, clays, and quicksands, of every thickness. They will need some magic to breathe, and more magic to move easily. Visitors will also be unable to see a thing. Elemental servants from this plane excel at missions in swamps. Wizards from the prime planes have been known to put their enemies into spheres, magically supplied with food and water.
Victims go insane from boredom.
Some explorers report a realm of clay near the Positive Plane, and a realm of silt near the Negative Plane. Some scientists wonder whether clays presented surfaces that helped with biogenesis on earth. The injured world of Athas is covered with silt. Some explorers report a realm of crystals near the Positive Plane, and a realm of frost near the Negative Plane. Caustic to organic matter.