Gehenna

The Bloody Field is the largest of the realms of The Abyss, occupying most of the Plain of Strife, an area approximately - and in as far as these things can be measured in the Abyss - the size of the entire dome of Aiaos. Much like the Grim Plain, the Plain of Strife is a reflection of the material realm in its rough shape, but not merely bleak, but broken and ravaged by millennia of constant battle in pursuit of the Deep War. Demonic forces wallow from the Spawning Pool and lesser Pits, while the armies of all the Nine Hells marshall in the Bladed Circle, to clash on the field beneath a blood-red sun.
The dark waters of the River Styx cut across the plain from south to north, forming a natural barrier between the two forces, but the demonic hordes press constantly to contest control of the field around the key logistical resource of the chasm of Escharon in the north of the plain, where the Styx plunges in an impossible cataract to the realms below. Beyond the chasm, the withering fires of Khorundam seethe.
Crossing the plain is next to impossible for a mortal, without a large supply of water and some form of transportation. The armies of tyranny and entropy ride terrible machines across the field, powered by captured souls, but the only waters are those of the Styx, which erode memory, self and soul with more vigour than they quench thirst.

Type

Dimensional plane