This Trophy / Achievement is obtained once you complete “The Prophecy” storyline, which consists of the two quests associated with the Hordafylke arc (In the Hall of the Slain) including:

• Where Legends Are Born
• A Brother’s Keeper

During A Brother’s Keeper you will need to fight Odin to proceed with the quest. You won’t be able to defeat Odin in combat, so instead you’ll need to do something unconventional: open your inventory and remove your weapon, which Odin is using to control your movements. You will then be able to run to the door and escape the fight.

Once you’ve completed both quests you will obtain the trophy / achievement.