The Blood Debt trophy / achievement is unlocked after you fight Thor during the Surviving Fimbulwinter main quest. This fight has a similar feel to the one at the beginning of God of War 2018, where Kratos fights Baldr. It is similarly lengthy compared with other fights, and there are multiple phases. It should be a fairly easy battle as one of the introductory boss encounters, but if you need help you can check our strategy guide on the Thor Boss Fight in Wildwoods page.

Blood Debt

Battle the God of Thunder