Locations: Velen, Elven Ruins
Since you can’t counter/parry Nithral’s two-handed axe, you need to roll/dodge his attacks. The idea is to let him attack first, dodge away, and delivering your own strikes. Furthermore, Keira’s magic helps a ton in winning this fight – if you utilize it right!
I also recommend applying Elementa Oil to your sword. The reason for this is that you need to get rid of Wild Hunt Hounds as soon as possible or Nithral will replenish a large chunk of his Vitality.
After he comes out of his protective shield and faces you, stick to the same strategy provided above and you’ll get him on his knees once again.
During this part of the fight, use Samum Bombs to blind the monsters and attack them from behind; especially the ones wielding long spears. Last thing that you can do to make this fight relatively easier even on Blood and Bones difficulty is to use Igni Sign Melt Armour ability.
As soon as Nithral emerges out of his protective shield, finish him once and for all!