User blog comment:Stacey aerist/young merlin vs old merlin in the finale/@comment-4650675-20121226135635

According to Balinor, the old man Dragoon is Merlin's strongest form, so that's why he became Dragoon to stop the fight at Camlann-he may have been unable to do so otherwise. If you look closely, Merlin's most epic spells have happened while he was Dragoon-generating a typhoon to attack Morgana, the lightning spells...almost all powerful ones.