Some examples for a common supernatural ballad motif with a quite broad dispersal (not limited to Northern Europe):
- Elveskud (Danish)
- Herr Olof och älvorna (Swedish)
- Olav Liljekrans (Norwegian)
- Ólafur Liljurós (Icelandic)
- Roi Renaud (French)
- Ann aotrou Nann hag ar Gorrigan (Breton)
- Heřman a Dornička (Czech)
There exist tons of scholarly debates on the inter-relatedness of these versions…
Scroll down on Christian Souchon’s web page to read about some of the theories.