Volgarr the Viking
20 Achievements
1,000
Xbox One
Xbox Series
By the Power of Gray-Skill..
Wield the fire sword
50
25.83%
How to unlock the By the Power of Gray-Skill.. achievement in Volgarr the Viking - Definitive Guide
Your equipment is upgraded as shield, helmet, and then sword. If you get hit, you lose the latest upgrade that you received. So, in order to get the fire sword, you need to have the shield and helmet upgrade and then get the next upgrade without getting hit.
You can see me getting the fire sword upgrade at 00:55 in the following video.