When you fight Bohan he will occasionally cunjure magic and attack you with it. If the magic is blue you can reflect it back to him by pressing Triangle as it hits you. If the magic is red you need to be in power stance and press Triangle as it hits you. If you never use the prompt to use the Circle button you can keep attacking and deflecting magic until you have a three glyph rating. This is an easy way to get a three glyph rating.