From where I re-enter Narshe to head and fight Umaro to recruit him in my party. After that I head my way to find Gogo, then I'll find Strago and finally Locke to complete the party for the final battle.
Boss Tips. His physical attacks are very powerful, so be prepared for a hard fight. I suggest you summon Golem for protection. He is weak against fire magic, but when he eats a green cherry, his attacks and defenses increase dramatically, so be very careful. After you beat Umaro, he will join your party.