Quote Originally Posted by Rosenstrauch View Post
By contrast, according to Emet-Selch the Ancients had to sacrifice their own lives so that Zodiark would do what was asked of him, be it ending the calamity destroying their world or restoring life to it. it's possible that, like Hydaelyn, Zodiark doesn't actually require this, but rather does it as a sort of equivalent exchange in order to avoid expending his own power. A being who values self-sacrifice as much as Hydaelyn seems to might see that as coveting power.
The first two sets of sacrifices were required just to summon Zodiark. The Ancients did not, to our knowledge, bribe him with souls as a means of securing his willing cooperation.

Quote Originally Posted by JeanneOrnitier View Post
We don't have a lot to go off of yet but I had assumed the root cause was the Ancients' creation magic. Fundamentally it's the same thing as the present's summoning magic, with the difference being that the Ancients had so much aether in their bodies that they could do it themselves. But if they did it so often, even for things like making clothes and buildings, then I'd imagine eventually they'd still start to hurt the world just like summoning too many primals does today. So I assume they put too much strain on the planet.
Information currently available suggests that the Ancients did not make any use of external aether whatsoever during the creation process. Everything they did was entirely internally powered. Furthermore, everything we know about the cataclysm they faced thus far is that it was geological in origin. Their powers became dangerous only after a sound emanating from deep within the planet caused them to go haywire.