Cania

The layer was marked by moving glaciers and icebergs that drifted as fast as a running person, constantly colliding with one another and with surrounding mountains of enormous sizes. Snow avalanches were common and violent. The weather was dominated by snow storms that howled with incessant winds. Thin layers of accumulated snow often hid deep crevasses that could engulf incautious explorers.
The supernatural cold of Cania was substantially stronger than in Stygia, reaching temperatures of −60 ℉ (−51 ℃), comparable to those in the Frostfell. It could quickly penetrate nonmagical clothing, freezing unprotected creatures within minutes and killing even those wearing gear designed to withstand cold temperatures in hours. Unsheltered creatures ran a constant risk of freezing to death. Preserved corpses were frequently uncovered after collisions between glaciers, while other glaciers seemed to hold unknown frozen creatures at their very centers. Some of the shapes within the ice suggested that they were archons or devas fighting unknown spined creatures, while others seemed like entire alien cities.
The layer was home of Mephistopheles and his keep, Mephistar.

Cold as Ice.