In Assassin's Creed Valhalla, you can find Offering Altars. On this page of the guide, you will learn where to find the altars. This will make it easier for you to max out the Suthsexe region.
You will find the Offering Altar in the southern part of the map, west of the synchronization point.
To complete this side activity you'll need 50 pieces of leather. You don't need to kill or chase anything, collecting the resource will be enough.