To the whole "how can you kill an immortal" argument, here is something I have to say. NOTHING is immortal because it is IMPOSSIBLE to prove that something is immortal. If by immortal you mean something that lasts forever then you most likely will notice that it is impossible to prove that anything lasts forever because you have to spend an eternity proving that. So in God of War everyone simply assumes that Zeus and the gang are immortal because they have lived for thousands of years and can do magic and crap.
Plus, another point to consider: what if immortality can be taken away. Just like Kratos lost his powers in God Of War 2, it means that immortality is powered by something, so if you disrupt that then you can kill an immortal.
Anyways, everything is immortal until it dies. So as far as I am concerned I am immortal. It is impossible to prove immortality but it is possible to disprove it, and to disprove it, you just need to kill whatever claims to be immortal.
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