Rygjafylke Hoard Map
"Hunters of silver-glory! East of Alrekstad, the hoard will look upon you from Torghatten Rock's eye. Engage its gaze and reap this reward."
Map pickup location:
Rygjafylke - Kjotve's Fortress
Inside a house
In the far west on the big island.
Underneath the western Fast Travel Point is a passage through the mountain.
The treasure loot is in the center of this passage.
Best way go go there is focus on the Cairns Mystery. Then the passage is right in your back.