A Part, and yet Apart

[Cilia]

With inter-dimensional and space travel possible in FF14's world, I can't help but wonder if Hydaelyn somehow crashlanded into Zodiark world and displaced him as the the world's crystal? Somewhat similar to FF9's Terra vs Gaia? Hence, all the Astral/Umbral Eras.

This is actually one of my current theories, with the added caveat that Hydaelyn is breaking apart tiny bits of Zodiark and using them as part of mortal souls. After all, the Ascians constantly refer what's known in Eorzea as a "Calamity" as "Rejoining" or "Ardor," and according to Sidurgu everyone has a tiny, healthy bit of void in them. The Ascian Prime also states s/he is going to make us "render our souls up to Lord Zodiark, that he might be reborn!" In this case, the Ascians' goal is to kill so many people that Zodiark is "reborn" and retakes his position as world crystal, thus making "everything as it once was, as it ever should have remained."

Another possibility I've come to think about lately is that Hydaelyn really is being a problem to the planet. This concerns the Astral / Umbral cycle. New thaumaturges are taught that the Astral / Umbral cycle is simply one of nature: a period of activity (Astral Fire) is followed by a period of rest (Umbral Ice). This isn't bad, or evil, or wrong, it's simply how nature works. Now, remember that the Sixth Astral Era went on for 1500 years, and the Seventh Umbral Era only 5. That's nowhere near enough time to balance things out. Without records there's no way to know for sure, but in the 3500 years between the fall of Allag (Fourth Calamity) and the start of the Seventh Astral Era, how many of those years were spent in an Umbral Era? How long does either last on average? Either way, Lahabrea's monologue after you defeat Gaius leads to the conclusion that something Hydaelyn herself is doing is messing with the aetherial flow of the world and throwing everything out of whack...

To this I would posit that Hydaelyn is forcing the world to stay in an Astral state when it needs an Umbral one out of the flow of nature, and this forced expenditure of energy is having a very negative effect on Hydaelyn (the planet), which is why Lahabrea says that "if the growing [aetherial] imbalance is not redressed, the very laws of existence - both physical and aetherial - will be warped beyond all recognition." Hydaelyn is forcing the planet to stay in an Astral state out of compassion for us mortals, but this is having an extremely detrimental effect on the world. (Thus turning Hydaelyn into a sort of Etro-like figure.)

It's doubtful either of these theories are right, but.