Fossegrim, also known simply as the grim (Norwegian) or Strömkarlen (Swedish), is a water spirit or troll in Scandinavian folklore. Fossegrim plays the fiddle, especially the Hardanger fiddle. Fossegrim has been associated with a mill spirit (kvernknurr) and is related to the water spirit (neck) and is sometimes also called näcken in Sweden. It is associated with rivers (Swedish name "Strömkarlen" means "The River Man") and particularly with waterfalls (foss in Norwegian) and mill races.

Description

Fossegrim is described as an exceptionally talented fiddler: the sounds of forest, wind and water play over his fiddle strings. Fossegrims can be induced to teach the skill. The Swedish strömkarl's lay is said to have eleven variations, the final one being reserved for the night spirits because when it is played, "tables and benches, cup and can, gray-beards and grandmothers, blind and lame, even babes in the cradle" will begin to dance.

Fossegrim is said to be willing to teach away his skills in exchange for a food offering made on a Thursday evening and in secrecy: a white he-goat thrown with head turned away into a waterfall that flows northwards,or smoked mutton (fenalår) stolen from the neighbour's storage four Thursdays in a row. If there is not enough meat on the bone, he will only teach the supplicant how to tune the fiddle. If the offering is satisfactory, he will take the pupil's right hand and draw the fingers along the strings until they all bleed, after which he will be able to play so well that "the trees shall dance and torrents in their fall stand still".^[2][5]