A plane? of extreme and hostile climates, composed of many spheres and layers. Though only three of these layers have been discovered, it is certain that more exist and just have not yet been discovered. The rule of the Abyss is the constant state of flux; doors open and close while minutes pass as seconds and then slow down to hours.
The first of these layers is a region of fire gouts, unceasingly burning flames and bubbling pools of scalding lava. Red-glowing stalagmites protrude from the ground, and a white mist manages somehow to linger near the center despite the heat. Blisteringly hot masses of blackened rock are strewn with charred pebbles and ensconced by a moat of molten lava to complete the searingly infertile landscape.
This white mist central to the Abyss shrouds a stable gateway from the Abyss to the Astral Plane, a near-polar opposite of the Abyss. The Astral Plane is a calm, tranquil place of washed-out colours and abstract dimension.
The other gate in the first plane of the Abyss is across the northwestern bit of the lava moat. Inexplicably, a monumental column of ice survives as a stable gateway to the second plane of the Abyss.
The second plane, as predicted by its gate, is a region of boreal temperatures and tundra-like ground. It is surrounded by frozen cliffs, and is sprinkled with glacial lakes. Much like the first plane, flames suddenly burst into existence and burn briefly (and frigidly, in this wasteland) before fading as quickly as they appeared.
The only known gate in the wintry level of the Abyss is an ice cave hollowed into the cliffs in the southwest corner, leading back to the constant blaze of the first plane.
A third level of the Abyss has been discovered recently. It is said to resemble the second level, yet be even more deadly.