The questions I want EW to answer the most: WHY and HOW was the world sundered?

[Alenore]

Are we even certain that there was a third party that caused the end of days? We know there was a sound, and I have always been under the impression that their fear of the unknown, through creation magic, brought about the end. Their fear gained so much momentum that they willed their own demise into existence.

It's entirely possible that I misunderstood it, but do we even know enough of the sound to be sure that it even was anything tangible to danger? Or was it just a sound?

There isn't really any indication that the Sound came from *something*. It may be a natural occurrence of the laws of nature ("Every 15000 years the aether resonates and the sound happens"), some unforseen effect of some rogue ancient's experiments, something doing it on purpose, the Ancients playing a bit too much with Creation (what if Zodiark was summoned to replace a previous Will of the Star which decided the ancients had to be wiped out?)...
We have absolutely no information and it's pure conjecture..

To add to the point Kizuya made, we have very little notion of what caused it, other than that a sound originating from the Underworld precipitated it. Fandaniel, invoking a seemingly ancient term like Telophoroi, is very much able to reproduce/reignite the crisis, so a possible manufactured (=caused by someone or something) origin is very much within the region of possibility. Even if it runs counter to my story preferences, I don't discount the possibility of them somehow causing the Final Days accidentally/in spite of their own wishes or knowledge (which would be tragic in its own right), but what I mentioned about Fandaniel is pushing me towards the situation being inflicted upon them, be it by a third party or resentful member of their own society, or even both collaborating. Something to bear in mind is that Venat's group had concerns about Zodiark, but it's never stated they were founded in fact, and if you wanted to plunge the ancients into a civil war to give the hypothetical cause of the sound a chance to return, whoever or whatever the instigator might be, exploiting such fears in a well-intentioned group is an excellent method of doing so. Were they to take Venat down the route of an antagonist, I'd imagine they'd opt for one like Yunalesca, where she had the best of intentions but at the same time tried to compel Yuna to fulfil her duties as she saw them, and go through with the Final Summoning. Hardly cackling villain material.



There is also Elidibus's 5.0 epilogue, where he claims both she and her summoners wish for the origins of the world to be concealed from the knowledge of the sundered. It is a monologue so we can take it that there is no element of deceit, and while he may be acting on the basis of flawed knowledge, it ties up with what Emet said and her own evasiveness on the topic. Furthermore, I wouldn't be surprised if it's knowledge he came about in his capacity as a mediator.

I'd argue that Fandaniel having to use artificial ways to mimick the Final Days points toward it being a natural occurrence more than something someone triggered on purpose.

To me, he's using the beings he enslaved in the towers to create nightmarish ceatures instead of the Ancients calling them forth. If there was abducted ancients stuck in towers or something similar, I think things would have happened differently pre-Zodiark.
If an illusion of the Final Days is enough to awaken the Echo, couldn't an illusion of the Sound (and we've heard weird sounds nearby towers) be enough to awaken this nightmare and thus, mimick the flawed creation given there's enough shards to do it? After all, if the vision of an end of your civilization is enough to let such a mark on someone's aether, wouldn't the thing causing all this destruction leave an equally profound mark?

As for why she wouldn't want people to know about pre-sundering, if she sundered the World on purpose to counter whatever threat or lock creation magick or whatnot, it would be quite counter-productive to let people know they used to be demigods able to conjure whatever they wanted. That'd be like telling a recovering alcoholic there used to be a better time when everything was greener. Some omissions are for people's good.