Some background to get you started. Here’s a general geographical view of the actual Myrka valley. The elements and themes are there to discover. I was surprised to see the number of variations (don’t know why, shouldn’t have been) but it’s a classic northern tale of grisly returns from the dead to accost the living. There’s a strong undercurrent of love denied / lust and death. To modern audiences the jarring thing about the story is the anti-romantic strain. Rejecting a love one because he’s dead seemed the right thing to do in the past but we tend to see death as an unwanted separation not a final crossing into the dark with a penchant for grabbing others to join us. Anyway, The story is tight and should lend itself to a 10 to 15 minute short.
Found this excellent storyboard by Hilda Torfadóttir from the Síðuskóla in Akureyri (1999), which just goes to show the story captures children’s imaginations.