The Hreidmar Palace Book Of Knowledge teaches you the Explosive Retreat ability in Assassin’s Creed Valhalla Dawn Of Ragnarok, provided you know how to complete that puzzle that blocks your access to the room containing the Wealth.
Since fighting your enemies requires all the help you can get, take the time to obtain this ability in the Gullnamar region. Later in your playthrough, you can upgrade the ability with another Book Of Knowledge found in the Svaladal area. But, for now, let us focus on the first one and see how to reach and complete the Hreidmar Palace puzzle.
Where To Find the AC Valhalla Hreidmar Palace Book Of Knowledge Wealth
You can locate the Wealth south of the Grenhellir Shelter, as you can see on the map below (almost on the south edge of the Gullnamar region).
The Skidgardr highpoint is the closest to the palace, so fast travel to it. Once there, look up towards the south, and you should see the destination far away on a mountain. Get on your mount and hustle up toward Hreidmar Palace.
When you reach the mountain’s base, you can use the stairs from the left. But that is a long way, so you might want to use the Power of the Raven to fly and get there faster (if you don’t have the power, there is a raven at the base of the mountain you can drain it from). Now, you don’t want to get all the way up; stop at the bridge that goes south and cross it. There, you will find the light beam puzzle.
Hreidmar Palace Light Beam Wealth Puzzle Solution
To solve the Hreidmar Palace puzzle, first, go to the middle and smash the crates near the reflector. Doing so will allow the light to pass through it later and drop a sphere on the ground (screenshot below).
Now, place the sphere on the pedestal near the door and aim it at the plate above the doorway, as you can see in the next screenshot.
Afterward, go to the pedestal near the bridge area and aim it at one of the reflectors. I don’t think it matters which one, but just to be sure, aim it at the one in the middle.
Now, you should be clear to enter the Book Of Knowledge Wealth room, collect your reward, and pet some cats while at it because why not?