Active only during the deepest nights of the winter, the Rime Wraiths are malevolent insubstantial beings that feed on the life of living creatures. The appear as nothing more than a low heavy fog with sparkling particles of ice suspended within them. They hunt only at night and during the worst winter blizzards, hiding underground inside the frost hardened soil itself during clear and sunny days. They are migratory predators, moving south with the spreading chill of winter and retreating north to rest within the permafrost through the hot months of the year.
A Rime Wraith will flow up around its victim and drain the life right out of them. They freeze solid , and the surfaces around them become covered in a swirling patterns of frost crystals, and the victims do not thaw completely until all of the frost and snow of the winter has fled the oncomming spring. Then they melt away into an organic sludge, nothing maintaining the solidity of their forms.. A Rime Wraith can enter buildings at will though a lit fire in a stove or or hearth produces enough heat to ward them away, as can a candle or a torch in a much smaller area. Only non-living heat sources seem to harm Rime Wraiths. Isolated Cottages have been found where the owners accidentally let the fire burn out over night and a rime wraith flowed in through chinks in the walls, freezing the inhabitants solid until well after the last frost had passed.
Rime Wraiths are not, as the name implies, undead, but fey creatures of deepest winter and thus bound by the same weaknesses as the fey, if you can find ways to apply them to a non-physical being. The only reliable way to destroy them is with fire, magical or otherwise and desperate hunters have been known to use prey staked out in the center of prepared firewood, or a well sealed abandoned hut that is then put to the torch to destroy a sorrow of Rime Wraiths.