To defeat bossses that cannot be harmed a lot from your gun or your dragon's wepon, turn your spiritualality up to max leaving your attack down to 0. Then use put a shield around yourself(after this is done you can turn your agility all the way up if you want) Anyway, after you have turned your spirit up cast a lot of berzerk attacks and now that your shield is up, you cannot be hurt and your berzerk attacks will cost less BP and be stronger!