Equilibrium must needs be restored [heavy sppoiler]

[Anonymoose]

We do. Remember the readings we were taking before we stumbled across poor Wilred? I'm disinclined to believe that dropping aether levels are entirely unrelated to the Ascians' plot. There could be some sort of entropy involved in dissipating primals, but it's hard to know one way or the other right now.

Considering that they were in the Black Shroud at the time, I've (for now) just been assuming that it's connected to the Odin storyline, where O-App-Pesi theorized that Zantetsuken reforged its own wielder by consuming ambient aether over an extended time. I think Odin's more important than we've been led to believe; even the 3.00 story invoked the Dark Divinity when talking about the true eikons. The drop in ambient aether seems (to me) more likely to be related to eikons than primals, now that we know the difference. On one hand, that quest did specifically say they were studying the impact of primal summonings on the aetherial balance. On the other, they clearly didn't know anything about the difference between primals and eikons until this patch, anyway. I'm unsure whether the observation supports anything they were looking for or whether they found it incidentally. It might have been the Calamity itself that siphoned Eorzea's aether somewhere else ("Yet even as it enervates, the Ardor empowers our master.")

The summoning and sustenance of primals eats up aether, but any in reserve that was not spent is returned to the land upon the primal's defeat. So any spent aether is gone, but whatever was ready to sustain it is still there or returned.

This is also possible, though I've been thinking of aether as raw energy; not created or destroyed but changing forms. To use Garuda as an example, if a chunk of the Land's aether were trapped in wind crystals, and then those crystals were consolidated into her form, and and then she expended some of it using her attacks, I just assumed it was no different than releasing the power of the crystals into, say, a synthesis. Energy converts forms, wind shows up, aether is freed and returns to the land.