Absolute Zero

The year is 2097, 20 years prior a large scale nuclear war took place. The entire world was sent into an indefinite nuclear winter. Due to this humans were forced into underground shelters along with people dubbed mutants. The "mutants" have special powers and are tasked with protecting the shelters. These shelters were built near underground thermal vents and hotspots. During the day humans and "mutants" can go outside to forage for supplies or to just see the sun for what could be their last time. Night is a different story though. At night temperatures reach Absolute Zero, a point in which the air holds no energy at all. This causes any living thing to die instantly, but the cold isn't the only thing you need to worry about. Some things have adapted to survive in these extreme temperatures. Things that will kill anything, animal, human, or mutant...