Viking: Battle for Asgard

I don't think it's possible...

Immortality use in this game means when you did you respawn like in one of the big Battles,
You die you get restored.
If you are aiming to get the Achievement "No Need For Immortality" You must not die during the last battle at Hel's Fortress, this includes not dieing up or fighting the final boss.

Not true, it only means dying up until the final boss

SPOILERS************************

When she turns into the giant thing u cant die, but thats not hard anyway, just use your ice power and run around her back, slash away until it say press B. But before that when u are trying to destroy the Shaman staffs u can die, i did like 4 times and still got the achievement.