Scathes are strange, bestial creatures of the icy arctic, who use their claws and skin-flaps to navigate the crevasces and plateaus of the icy plains. Related to the harriers of the tropics, they have keen senses, and hunt nearly anything that enters their territory.
The pallid, white, leathery flesh of a scathe makes it difficult to see against a background of ice and snow, particularly in the darkness that they prefer to attack from. They are concealed against darkvision, even, rendering it ineffective. They hunt in packs, and employ poison in their strikes that cause distracting (though not debilitating) pain. They're also immune to cold damage, as befits their arctic surroundings.
Scathes are rather vicious creatures, but that viciousness has a use: scathes (or their wormlike larvae) are worth quite a bit of gold to a prospective buyer as a guard-beast.