This whole time, I thought Hydealyn was the Source, and Zodiark the moon... after rewatching some cutscenes, I'm starting to believe it's the opposite.

Elidibus goes on about "will of the star", and the first moon cutscene we had back in Heavensward we assumed Zodiark was the moon... but Shadowbringers revealed that Light is more attuned to stasis, as the Moon (it's also a white ball of light) while Darkness is shown as active and chaotic, the Source and the other sundered planets. The Ascians bring a rejoining by sacrificing those sundered worlds to the source, to make whole. If the source was made whole again, Zodiark would reawaken and have that fated rematch with Hydealyn.


Even the painting and diagram shown by Emet Selch gives us clues, of course they wouldn't just tell you outright as it could very well interfere with their plans.

Possibly if we finish off Elidubus before he's able to rejoin another world, he'll somehow revive Zodiark prematurely out of desperation, but it'll be just powerful enough to give us trouble.