Baator

The Nine Hells of Baator is an Outer Plane, and the birthplace of devils. Filled with smoke, fire, and ash, each Hell save the first is buried deeper underground. These continent-sized caverns contain fiery infernos, frigid wastelands, poisonous mires, and cruel fortresses, all of which are terrible beyond understanding. Only the greatest - and most foolhardy - adventurers dare to venture into this plane.