I've read a lot of interesting theories on here about the Ascians, but there's something that stands out to me.

Mostly it's Faith, and how beliefs (or perspectives in general) seem to be a running thread in the universe, from Ascians declaring themselves true believers of Zodiark, to the line about how "We must believe we can achieve something, whether it's true or not."

Maybe Zodiark and Hydaelyn could be separate aspects of the True God, but only by the "Rejoining" could this God return?

All this talk of the Moon and the Star, yet nothing of the Earth?

Nothing but speculation of course, but I honestly believe that there's another God (neither Good nor Evil, but definitely not Neutral).