Acedia

The 4th layer of the seven hells, the layer of sloth. Due to the nature of the archdevil ruling this layer, it is a rather peaceful place, at least in comparison to other layers, where creatures can rest and sleep... eternally.
Acedia is a frozen landscape of ice and snow. Only the large central lake is unbothered by the cold.

Features

Acedia's Curse

An energy-sapping atmosphere pervades in Acedia. At the end of each long rest taken on the plane, a visitor must make a DC 10 Wisdom saving throw. On a failed save, the creature gains one level of exhaustion, which can’t be removed while the creature remains in Acedia. A creature that reaches six levels of exhaustion while on this plane doesn't die Instead, the creature turns into a devil under the command of the archdevil ruling this plane, whereupon all levels of exhaustion afflicting the creature are removed.