There are 16 legendary animals in Red Dead Redemption 2. They will require a good deal of tracking, hunting, and baiting to appear.

You need to hunt them if you want to craft specific items. Skinning them will yield a legendary pelts, which can be traded with the trapper to craft special and unique outfits. They can also yield fangs and other items that can be traded to procure rare talismans that boost your powers.

How to kill the legendary animal in Red Dead Redemption 2?

...