Tips vs Thrym Winterhowl (Ice weaving)?

The spellweaving quests tell me to defeat Thrym Winterhowl in Ravenscar six times... I can't even beat him once! He gets a free cheat attack (Storm) every round; after about five rounds, he gives you an Ice treasure card to use, but it doesn't kill him... it just removes his blades. And if I kill him with regular attacks, it resets him to full health! Ive had no luck getting a team-up group, so I'm stumped. Suggestions welcome.