Originally Posted by
Cleretic
Before Zodiark, the Ancients were basically defenseless against the End of Days specifically because of an inability to interact with dynamis. Because they couldn't turn that energy in their favor, it meant that everything they created were sitting ducks prime for dynamis corruption--and the Ancients do a lot of creating. So even with the Ancients not knowing what would await them if they pursued Meteion, it was a fair assumption that just turning up as Ancients would go poorly.
Of course, when we went to Ultima Thule, we learned that assumption was very much correct, because it turns out the only means of survival and traversal was through dynamis manipulation. First Thancred making the space actually baseline habitable, and then by interacting with Ultima Thule's inhabitants to counteract their corrupt dynamis preventing further traversal. Of course, it's not just dynamis manipulation that was needed, but also personal experience to speak from, but the former was just as required as the latter.
Dynamis was literally mandatory for humanity to fight Meteion and truly stop the End of Days rather than just blocking it. The question of whether fighting Meteion at all was necessary after Zodiark got put up is still an open one, but a certain Fancy Daniel forced the issue there.