Jack couldn't keep on being passive anymore in this valley as it would take too long of a time for them to complete the quests otherwise. Not to mention that the others were having trouble fending off these flying monsters. When Jack started sending his attacks, the Green Harpy and Bald Eagle started to fall down in droves. These monsters were high level compared to the other field monsters they had encountered, but their HP was comparatively low, probably compensating for their flying ability. Hence with Jack's high damage, it just took him a few hits to kill one harpy or eagle.
Jack could feel the respect in the glints of his team members' eyes, except Warpath. The guy still had the illusion that he was the main character. He kept on chasing after the Green Harpy, who flew low, bringing him away from the team. Suddenly another Green Harpy swoop in from behind. Its two large claws grabbed onto Warpath's shoulder.