I found it easiest to get hit until the prince of darkness destroies the cannon, to just hit him untill the helmet disapears. then equip lightning(or is it thunder) and sheild. When the laser guns comeout use lightning(or thunder) and destroy them and keep hitting him with the sheild on, to protect you from the saw. I also recomend that you fill up the heats to max. Keep an elixar and the best potion with you and refill only when you health is at the lowest possible.