Twisting Nether
The Twisting Nether is the astral plane between worlds and it is frequently described as the place between the ebb of Light and the flow of the Void. Supposedly, long ago there was nothing but Light and Void, and the two eventually collided to create the Nether. Due to the nature of the Nether, there is no one true way to perceive it, and those that bear witness to the chaos that connects the worlds of the universe will all see it differently. After all, it transcends all laws of reality and time, and space, operate differently within it.
Origin
Long before life existed as it does in the modern age, there was simply the boundless sea of living energy that was known as Light. However, Light could not fill every crevice of the universe, and thus where it could not reach there were pockets of pure, cold nothingness that eventually became what would be known as the Void. Over time, the Void began to grow on its own, and it moved against the Light. When the two collided, a great surge of energy was released, which tore open the very fabric of creation and ultimately gave birth to the universe and the worlds that inhabited it in a great maelstrom of fire and magic.
Unstable energy ultimately coalesced into its own dimension where Light and Void collided and bled into each other in a tumultuous storm. This plane, which would become known as the Twisting Nether, gave birth to demons, and occasionally tore through the veil of reality to spill its creations into it and warp the very essence of creation.
Geography
The Twisting Nether is everything the universe is not. While the universe is bound by physical laws and rules, the Nether is the pure chaos that binds it all together. Thus, artifacts of reality can be seen within the Nether, such as pieces of shattered worlds drifting on tendrils of energy. However, everything is spectral, muted, and seems to bleed like a haze across it. Colors can change, it can go from light to dark in the blink of an eye, and strange sounds may occur only to vanish as if they had never happened. Time has no rules here, for centuries within the Nether can be but a few minutes in reality. Ultimately, it is intensely magical, and there does not seem to be any rules to its geography save for those a traveler makes for it.
Ultimately, the Twisting Nether is infinite in size and has no borders and no end.