For Vanaheim! is a Favor side quest in God of War Ragnarok that takes place in the Vanaheim Crater. The quest starts automatically after you complete Scent of Survival, which in turn can be started after completing the Creatures of Prophecy goal on The Path main story quest line, by following Helka the Hound out of Freyr’s Camp. You thought Birgir had died when he fell from the paper boat, but Helka knows better, and these side quests are all about finding and rescuing him.
How to reach Birgir’s location
After you’ve completed Scent of Survival and taken another ride on the paper boat, you’ll find yourself in The Vanaheim Crater. Birgir’s location is on the far side of that huge frozen lightning bolt, but you can’t get to it just yet.
Drop off the ledge, then immediately turn left and drop off another ledge marked by a torch. Go across the flat area, then follow the ledge to the left. Jump across the first gap, then swing across the second and follow the ledge north. Climb up then head northwest, and Atreus will spot an altar.
Continue northwest along the edge of the area with the large pond, then take the north path (watch out for exploding plants) and follow it until you reach a cave. Swing across the cave, ignore the vine plants for now, then swing across the next gap. Climb the high wall, then follow the path southeast to the Celestial Altar, and use it to change day to night.
Drop off the ledge to the east, then turn left and defeat the ogre banging on the gate. Go through the gate, follow the path, and turn right down the slope and under the narrow arch. Squeeze through the gap and defeat The Crimson Dread.
How to rescue Birgir and send him through the Mystic gateway
Climb the wall on the east side, then enter the ruin and speak to Birgir. Go southwest and interact with the Mystic Gateway to send Birgir through it. He’ll give you the Rond of the Nine Realms before he leaves, and the quest will be complete.