The twist is definitely original and brain-racking. There's a nice balance between what seem like normal boss attacks, and a challenge in getting yourself hurt. Perhaps, if the MC seemed happier and bloodier as she got damaged, it'd have completely sold the idea.
The story is impressive, time was definitely well-spent in that regard during the week. The nordic mythos is always a delight (goofy bosses aside). The art is great too, and the choice of font.
I recommend using more transitions (fade-in, fade-out, etc) just like in the intro sequence, just to avoid the sudden appearance of things and the abrupt change of scenes.
Amazing job!