To easily defeat Cerberus(dog with 3 heads) first wait until he is about to do the attack where he barfs up dark magic. When he does this, he arches his back. Try to jump onto his back. If you succeed, he will not be able to hit you with any of his attacks! At this point you should wait until he does his biting attack, then jump down and attack one of his outer heads. Repeat this as needed until he keels over.