Originally Posted by
Cleretic
So then comes the question of how, and the 'how' is the big enigma. We know that there comes a point where Zodiark is strong enough that he can be awakened and used for this; Hydaelyn in the post-Antitower scene implies this point is after the Eighth Umbral Calamity, but we know that explanation was a bit fuzzy, and the Tales from the Shadows short story doesn't suggest that the Ascians are active in G'raha's future. That might mean that they still had to do more Rejoinings and it's just that the Eighth was the last chance to stop them, or it could mean that they're just off doing something else that Omega isn't privvy to in that story--perhaps that getting Zodiark functional requires a few more steps, maybe something like 'he needs more sacrifices and there ain't enough on the Source, let's go drain the Fourth'. No matter what, Zodiark is eventually an active factor. We know from the Void quests in Shadowbringers' patches that fixing the Thirteenth is possible but slow; that sounds exactly like something you get Zodiark to shortcut, but it also might possibly not be necessary for them to fix it in the first place. We do know that we've never seen any evidence of them trying to fix it though, which lends credence to the theories of either 'they can't right now' or 'they don't want to'.