The Blacksnow Charms are charms worn by Space Wolves, as a memento of the victory over an Ork Waaagh! that ravaged the ice world of Geot.
When the Space Wolves were done with the Orks it is said that the snow itself was turned black by the ash and filthy smoke of thousands of burning Ork vehicles. The Blacksnow Charm contains a few crystals of the blackened ice, kept at permanently frozen temperatures.
Sources
- 1: Deathwatch: Rites of Battle, pg. 157