one of the main ones is that you need it to be able to capture Bernard when you are a werewolf if you go the normal logan path, another is to capture ratkings, lizardmen, werewolves, and maybe in the future some other little thing
you can also capture Logan during the Bernard route if you tell him that your out of wolves bane. it will cause him to ditch into the forest, you can also take Rhoushk home and Rhot if you do the corrupted lizard path.