Complex sentence: In fact, the intense battle between the two Sea Lords lasts for days, and is so vicious that it creates destructively violent storm waves and tsunamis, though the true winner of this battle is never specified but theoretically it was Poseidon.
Split into simpler sentences: In fact, the intense battle between the two Sea Lords lasts for days and is so vicious that it creates destructively violent storm waves and tsunamis. Though the true winner of this battle is never specified but theoretically it was Poseidon.