Herr_Magnus_og_Bjærgtrolden
Hertig Magnus och Hafsfrun
Medieval Swedish/Nordic ballad
Hertig Magnus och Hafsfrun (Sir Magnus and the Mermaid) is a medieval Swedish and Nordic ballad and an 1867 operetta with libretto by Frans Hedberg and music by Ivar Hallström about the insane Swedish duke Magnus of Östergötland. [1]