Been listening to Myths and Legends. @mythsandlegends@twitter.com goes into legends beyond the just well known (e.g. Greco/Roman or Arthurian). His critiques seem apt, but where it really seems to shine is the attempt to fill gaps in motivation.
I have never heard of Koschei the Deathless and he explains that he takes some liberties in trying to figure out the motives of this sorcerer. The result is haunting and amazing.