Dark Gaia Phoenix will first fire feather arrows at you. Dodge them and quickly determine his next location to attack. Follow it and jump on the platform (pillar-type structure with a water barrel) nearby. To defeat him, wait until it’s done attacking and pick up a water barrel. Throw it directly at him when it hovers around the platform. Next, he will fly to the center of the battle arena. This is your opportunity to attack him while he rests. Repeat the process until he is defeated. Note: He’ll be more resistant to the water barrels the more he’s attacked.