Good and evil.

Well, I wouldn't say that good and evil are so relative. In principle, it's clear that killing creatures for fun isn't right. By the way, according to Christian doctrine, evil is merely a byproduct of free will – the highest gift from God to people (and angels; the final decision regarding animals has not been made). Thanks to free will, people can independently make a moral choice between good and evil; that is, they can live. Live as independent and free beings. Evil only provides this possibility of an alternative.