I'm almost sure that it was said during the game but I can't remember pretty well. I think after the death of 90% of humankind by Asmodeus virus the Light Gaia army and the Dark Gaia monsters fought in the south pole. But what happened then? I know the former hero (light Ark) was killed and his armour and spkire were sealed in a box by Light Gaia waiting for his resurrection and hidden. After that, it was found by Columbus and delivered to the village of Stockholm.
But I though before the world was destroyed (came to the state we see when we arrive on surface) in the war. That way Columbus could not have done all this stuff. Otherwise, if it was not destroyed how have the world became in such a calamity state? Who transformed the living beings into fiends? Who sealed the Dark Gaia in the underworld? If it was the Light Gaia, why not to do it in the beginning of all this mess?
And, at least, why have the five continents be submerged and who did it? After all, I've thought the objective of Dark Gaia was to help Beruga with the immortality stuff and stop the time clock at 13. If the continents were to be submerged and Dark Ark not created by the Devil, things would be that way eternally. The clock would not be stopped at 13 but would be stopped the hour messing up with the balance anyway.