
Originally Posted by
Alenore
They need Hermes to know where it comes from. Except Venat already knows, since we told her what the Watcher told us. They only need Hermes if Venat decides not intervene in any event, and keep to herself what she knows from the future.
As for Meteion, stopping her before she reaches Ultima Thule, certainly not. But devise a plan to fix the issue, as we did, in time? Most likely yes.
I guess that's what bugs me: why wouldn't she use what she knows of the future events? If that's to make sure our timeline is conserved, then they did a poor job explaining it in game, but that'd be a valid justification: "I acted in a way, these people now count on me, let's make sure this timeline and these peopls are saved".
But she could as well just try to save her timeline, and hope for ours to survive (just like G'raha's 8th calamity timeline still goes on, not that anybody knows it in-universe).
As for Dynamis, Hermes is not the only person knowing about it. He mentions it's not a common subject (during the Gobbue cutscene in Elpis), but some scholars are acquainted with the theory.
In over ten thousands years, one could probably rise to the occasion and actually reach some conclusion. Hell, Venat probably could considering she managed to design the plans for an interstellar spaceship and a spell to sunder reality itself. She seems quite adept at mastering new fields.
I don't think they were prepared to do the third sacrifice. Even if not taking the whole cutscene where she sunders the world at face values, it would be the 2nd: the Final day weather is still around, and they intend to insufle the world with new life. The plan for the third was waiting for the new life that was the result of the 2nd sacrifice to grow, and then sacrifice part of it in exchange for the souls.
The Ancient praying to Zodiark even proposes lives, to get back their perfect paradise. Not to sacrifice part of this paradise in exchange of the souls.
In any case, the timeline of these events is at best blurry, not less because the "Thou Must Live, Die, and Know" cutscene seems to be very open to interpretation.