Ice Geist

Description
When a group of travelers became stranded on a dangerous, snowy pass with no way to escape, sometimes they would turn to murder then cannibalism. These evil deeds tainted the terrain around it and the souls of the unfortunate became a single powerful, undead entity: an ice geist.

An ice geist appeared as a huge, black cloud with screaming humanoid faces boiling to its surface. Supernatural blue light flashed through it like lightning. As in its last moments, the geist still hungered for bloodshed and the flesh of living things. It sought other creatures who shared in the same misfortune as it did. Living creatures killed by an ice geist joined its cloud, adding to the fiendish cloud's strength.

Undead Nature. The ice geist did not require air, food, water, or sleep.