Battle with Ba Ganman and his cronies in the Nam Yensa Sandsea, when you initially accept this hunt from Montblanc, he goes under the pseudonym of Belito. He is also the guy who chased you out of the Lhusu Mines during the earlier part of the game. Also if you have Balthier on your team, they will direct practically all of their attacks at him, a bit like Lani did to Garnet in Final Fantasy IX, this therefore is useful, as the other two characters will take less damage generally. Obviously you should take out his henchmen before attacking Ba Ganman himself.
