Once you reach Angri-La and progress the story as far as heading off to the mountain with the High Lama, return to where the Priest is to find a man looking for assistance.

He asks you to head outside to the Slopes and use the Pep Power Blaze of Glory against a Boreal Serpent. Simply head outside, defend in battle with the Hero and Hendrick are both Pepped Up and then unleash Blaze of Glory before defeating the Boreal Serpent.