Have you ever wondered why moogles became extinct and the lost civilization at Goug mysteriously vanished? I'm currently working on a rationale as to why moogles no longer existed, and believe me, it's not easy. I mean, the game does not go into detail about moogles at all. The only thing I can do is find clues and draw up inferences.
Ok, now I'm going to get into the meat of my post. So, how does a well-developed civilization, with technologically advanced weapons and machinery, just fade away? After some thinking, I came up with a theory: one of the holy stone's power, unleashed by an unknown entity who consistently abused its power for personal gain, destroyed the whole civilization, as well as the people who inhabitated it(remember, the stone's actions are dependant upon the person's heart). It may sound silly to some people, but you have to consider two things: 1) What the holy stones can do. We already know they transformed humans into zodiac beasts, revived Malak from the dead, conjured up a wave that engulfed some king's castle(I know the description is vague. I think I read about this in the Germonik Scriptures. Could someone inform me if my interpretation is incorrect?) and, amusingly enough, talk. Who knows what else they can do? 2) The holy stone's prevalence and utilization during that time period, as evident in Worker 7 and Worker 8. Therefore, because of the accessibility to the stones, using them for the wrong purposes is more likely, resulting in a devastating scenario.
As I understand, FF12, which I have not played yet, is suppose to be Ivalice's past, so maybe that game could give us more information. Anyway, post your comments/thoughts and theories on these topics.