Heroes of Redcoast City
Its geography is mainly rocky, with the occasional lava river, or acidic goo puddle. While traversing it the temperature continuously switches from being just hot enough to be uncomfortable to just cold enough to be uncomfortable. The whole plane is lit by a green sun.
The Demonic Plane originated as an innovation in the private prisons system, as a pocket dimension that would slowly preserve the life and harness the life energy of anyone imprisoned in it. The inmates were left to fend for themselves, with minimal oversight or expense needed, and big, guarded, “dimensional relays” were placed through the plane to convert the life energy (that the plane’s lay-lines harness from the inhabitants) in electric power and send it through our world.
After a year or so though, the effects of the continuous resurrections and the life-energy absorption started to became evident on the inmates. As time passed they started to look more and more like magical abominations, and less and less like humans. Soon, the relays were destroyed by the frenzy of the now beastly inhabitants of the plane, and the company who developed this system decided that trying to keep hold of the pocket dimension was more bother than it was worth.
The project was closed, and what isnow known as the Demonic Plane remained as an endless valley of violence and despair, completely cutoff from the world’s daily reality.