Carceri

Carceri, or the fourth layer of the Nine Hells, was an Outer Plane that embodied torture and slavery above all else. It was home to the Prime Evil Torog, and was a blizzard-blasted wasteland said to be held together by massive iron chains. Evil creatures, or those hapless enough to be trapped there, were imprisoned in Carceri by legions of chain devils, endlessly toiling in the icy wastes for some unknown purpose.