This quest becomes available once you complete Reporting on Cent. To begin, you should go to your quarters and rest in your room (use the bed) to initiate a cutscene.
When the brief scene ends, Eivor will awaken to Dag calling outside. Meet him there to begin another cutscene, during which Dag voices his discontent with Eivor, and demands a fight to the death. You will have three dialogue options here, but regardless of which you choose, the outcome will be the same. You must fight Dag.
Boss Fight: Dag
The fight with Dag is confined to a circle created by residents of Ravensthorpe. You needn’t worry about harming them with stray arrows or poorly struck melee strikes. Despite his size, Dag can be quite swift in his movements, especially when evading your attacks. You’ll find that he can easily dodge most of your light and heavy attacks if you strike when he is in a defensive stance. As a result, the best time to strike is just after you’ve parried one of his attacks, while he’s vulnerable, immediately after dodging one of his attacks, or just as he executes one of his attacks. This will almost always ensure at least two hits before Dag resumes a defensive stance.
Almost all of Dag’s attacks can be parried or blocked. He only has one special attack, which is essentially the same as Eivor’s Dive of the Valkyries. When Dag is about to perform this attack it will be indicated by a red rune aura around him, as with most other special attacks. He doesn’t have the ability to heal, and he can be made vulnerable by hitting his weak points on his right shoulder, left hand, and left knee. When you hit these with your arrows and perform a stun attack, you’ll take about a quarter of Dag’s health. At this point he will drop his shield and begin dual-wielding axes instead.
You will find it relatively easily to avoid Dag’s basic attacks if you’re not too confident in your timing with parries or blocks. Just continue to walk around him and backwards. After the attack, he’ll be vulnerable to a flurry of your own. You may want to perform a dodge or a roll to avoid his special dive attack, although this can also be avoided if you keep moving around him.
When Dag is around 35% health, he’ll remain on the floor for a few brief moments while Eivor offers him exile. When he refuses and gets up, he’ll attempt to throw an axe at you, so be ready to avoid this. At this point he will also begin to include a flying kick in his attack rotation. This can be more difficult to avoid by simply walking around him, so you may want to use dodge here to move out the way. This will prove even easier if you have the Brush with Death skill. After the attack Dag will be vulnerable to a Stomp attack for a brief moment, so be sure to stay close to him to capitalize on this.
Decision: Give or Deny Dag his Axe?
At the end of the fight you’ll need to decide whether or not you should give Dag his axe. Odin will present himself at this point, attempting to persuade you not to give Dag his axe. However, if you want the best ending to the story you should give Dag his axe. If you don’t, Sigurd will not be pleased and the best outcome cannot be achieved.