Doesn't matter if you die against eikthyr. Just go touch your gravestone and the corpse run buff will give you the staying power to just punch the boss if you want, die again and just keep doing that, I did this with a naked character and a flint axe so I'm sure you'll be able to this in less deaths. I wouldn't recommend this with any other bosses though, strength goes up considerably and corpse run buff won't protect you too well outside of blackforest.