What is "frostfell"

In the Dungeons & Dragons fantasy role-playing game, the Frostfell is a polar area that almost always experiences extremely cold temperatures and frozen precipitation, as described in the supplement Frostburn. In the Eberron campaign setting, Frostfell is a specific region that lies at the northern extreme of the world, separated from Khorvaire by the Bitter Sea. It is a place of eternal ice and snow, mostly unknown and seldom visited by mortals.