From Grizzlies West Snowy Peak dreamcatcher head northeast down the hill until you reach the trail. Head north on the trail. Skip the first fork that is a dotted line on the map. Take a right at the second fork heading east. The correct trail will be a solid line on your map. You will eventually see a campfire and tent to your right. A little ways after that there is a log sticking out above the trail on the left. Turn left up the hill immediately after the log. The dreamcatcher will be in the big tree right behind the log and a small stump.
Finding all 20 dreamcatchers will reveal the location of the Ancient Arrowhead treasure; A unique item that makes Arthur's stamina last twice as long when using the bow.