Ice Bogie

A gaggle of mischievous, rime-covered humanoids, one of which is standing on the shoulders of another, paint hoarfrost patterns on a window._
Wherever the temperature drops below freezing, mobs of ice bogies may appear to unleash their wintry mischief. Enigmatic creatures of ice: the hows and whys of their random arrivals remain a mystery. A group might plague a remote village for an entire winter or pester a yeti for a single afternoon. Whenever frost forms in suspicious places or patterns, ice bogies are likely to blame.
Japes and Vandalism. Whether pilfering innocuous items, laying slicks of frost across doorways, or freezing a goat’s eyelids shut while it sleeps, the creatures find delight in pranks and making nuisances of themselves. Capricious and gleeful, they are equal opportunists—seeing little difference between humanoids, beasts, or monstrosities. They find pleasure lurking on the edges of civilization, gathering to play their tricks on unsuspecting pioneers before melting back into the frigid wilds without a trace.
Vicious Reprisals. While ice bogies are known to occasionally help lost travelers or return stolen prizes the next day, they have a dangerous side. When provoked, they swarm their opponents in a series of darting attacks from all sides and are known to pelt their enemies with shards of ice plucked from their own bodies in a flurry of hail.