Ooh, I love the Nibelungen saga!!!!! :)
And yes, you did understand it right, it's a very good and adequate translation, as far as I'm competent to judge this. The only thing that comes to my mind is this line:
'But invincibility is a challenge' Perhaps 'invincibility is THE challenge' would make it a bit clearer. Otherwise, I really like it!! :)
EDIT: Oh, and with our recent forum discussion in mind - 'Und doch wird er unsterblich sein...' in this context, song, perhaps 'shall' could fit well -> 'the hero shall be immortal'?
Suggestions are always welcome
Vorschläge sind immer willkommen
This song narrates a story arc out of the Nibelungenlied. See wikipedia article: http://en.wikipedia.org/wiki/Nibelungenlied