Protagonists are always loners, almost by definition.
A lone wolf in the group, this horse is aloof and wise.
protagonist | prōˈtaɡənəst, leading character or one of the major characters in a drama, movie, novel, or other fictional text. • the main figure or one of the most prominent figures in a real situation: in this colonial struggle, the main protagonists were Great Britain and France. • an advocate or champion of a particular cause or idea: a strenuous protagonist of the new agricultural policy.