The Infernal Planes are separate and wholly unique from the Material Plane, born of the evil thoughts of the world-mind, and bathed in the most wretched side of law and chaos. The Infernal Planes hold the infernals, beings of pure, unadulterated evil bent on their own vile selfishness and personal gain. The planes themselves are unique from each other, but connected through their similar alignment of conscious thought and vile origins. The planes are split down equally between law, neutrality, and chaos, though the scales of power tip towards the rule and organization of law. At an unknown time, whether during the very creation of the planes themselves, a more recent but still ancient past, or in the current era itself, the infernals known more widely as devils came into power over those known as demons, and hold their more chaotic brethren as a hunter holds the leash of a hound.
To the minds of the most well-studied and perhaps crazed scholars, the infernal plane is a source of near unlimited wealth and power at a cost far greater to the mortal than the immortal. Souls are the currency of the infernal planes, and the most popular cost of any deals struck amongst the denizens within. The planes themselves are lands of unknowable torment and horror, from the very heights of pain and psychological torture, to the deepest depths of sensory deprivation. No mortal who stays for long remains as they once were, with many of the greatest villains through-out history holding origins as valorous heroes delving too far into these twisted planes.
The infernal planes originated from the very creation of the world.