So aether, how does it work exactly?

[Cilia]

Well, far as I can figure... aether is like a combination of matter and energy. Therefore it behaves like both and neither.

Remember, energy cannot be destroyed - it simply changes form from usable to unusable. Sunlight helps grow trees, which can be burned for energy, leaving only unusable ashes. In the world of XIV, this is simply not true - aether changes from one element to the next, spinning on the elemental wheel observed as a part of the UI in Eureka.

That's not to say aether can't become unusable - corrupted aether and crystals are highly volatile and can't be used for anything but disrupting other "normal" types of aether, such as when it was used to help breach Garuda's barrier and endure Leviathan's Tidal Wave on the high seas. If corrupted aether then transitions into a usable state... well, that I'm not sure of.

Either way, one of the major reasons primals are so dangerous is that they introduce true entropy to Hydaelyn - the aether that makes up their physical form returns to the land when felled, but any other aether a primal consumes while on the material plane is simply gone or otherwise converted at a very poor rate into loose aether upon their defeat. (Case and point: Bismarck, known to eat islands in the Sea of Clouds, leaves nothing behind upon death but the key to Azys Lla. Why wasn't that destroyed? Plot, I'd wager.)

It's also scientifically provable that aether levels across Hydaelyn have dropped through the ages, evidenced by Matoya's Crystal Eye (an ancient Crystal of Light) and the Crystals carried by the contemporary Warrior(s) of Light. This is implied to be due to Calamities and primals; where the aether is going isn't explained, but can be presumed to be going toward awakening Zodiark.

As Moose-senpai said, a Flood of Light or Darkness can also destroy aether - Dark compresses it into a singularity, while Light bleeds it away into nothingness.

That's all the information I have on aether, with a little bit of extrapolation by YT thrown in.

[Anonymoose]

Well, far as I can figure... aether is like a combination of matter and energy.

Æ=MC²

Problem solved!

[Cilia]

Let's take it one step further...

The various elements have different energy charges, depending on where they are on the elemental wheel. Astral elements will naturally have a higher energy level, while Umbral elements will have less; more accurately, Astral elements generate energy, while Umbral elements absorb energy. Lightning, or plasma, is the most powerful state of matter in existence - so great atoms are being ripped apart. (The Sun itself is a giant ball of plasma.) Ice, or more accurately cold, is the state in which matter has the least energy in it - it will consume any energy it can to change its state to a more energetic one.

All of the Astral elements (Wind, Lightning, Fire) are ephemeral and cannot exist in a solid state; they must lose energy and turn into an Umbral element (Earth, Ice, Water) to do so.

... with the exception of elemental crystals, of course.

As for immaterial concepts (thoughts, memories, etc.) - yes, they exist, but only as aetherial fluctuations, not aether itself. Auracite works by attuning itself to an aetherial wavelength (say, B'gamnan's desires or the original Ramza's personality) and then does something with it; the Duma makes the user's desires manifest on the physical plane, while the Otius is a sort of aetherial floppy disk containing the original Ramza's personality. (Someone correct me if the Auracite Ramza picked up during the Ridorana closing scenes was actually the Duma.) This is how Fordola's Resonant Echo allows her to fight Ultra Instinct style - it picks up on the aetherial fluctuations of her opponent(s), allowing her to react before their attacks are launched. Aside from Urianger's Aetheric Burst tool, theoretically it could be overcome by simply quieting one's soul so there are no aetherial fluctuations... or simply by fighting so recklessly your attacks couldn't even be predicted by yourself... but I digress.

Æ=MC²

Problem solved!

Amendment:

Æ=(MC²)*e

... where e changes depending on the element, with Astral elements having the highest value and Umbral elements having the lowest (possibly even negative).