Fossegrim

The Fossegrim is a water spirit, or troll, from Scandinavian folklore.

It is found near a North-flowing waterfall, and the music from its fiddle would cause anything with limbs to dance. the young and the old, the well and the ill, even trees and furniture. This fossegrim wears a blue robe that reflects the river that he resides in.

It wears a wooden mask to hide its face from mortal men. It grasps a fiddle, poised to start playing when it sees fit. A fossegrim would teach passers-by to play the fiddle for an offering of food. But it would only show how to tune one if the offering wasn't big enough.