[Ongoing Thread] Endwalker Lore Questions [Spoilers]

[Loggos]

After finishing EW I have a couple of lore questions but instead of making a thread for every single one of them I thought I could just start an ongoing thread in which players answer each other's questions.

So everyone else who has lore questions, feel free to just ask them here.

Obviously this thread is gonna be full of spoilers!

My questions:

1. So why exactly was Zodiark needed?

On the moon we get an explanation about the aether flows/streams/nets engulfing the planet (I play in German so I don't know what the game calls them in English) by the moon warden.
S/he says that the outer "streams", the astral streams, were damaged during The Final Days.
At places where the streams were particularly damaged, the effects of The Final Days manifested.

To this one NPC (I forgot which one) says something along the line of
"So they created Zodiark to repair/balance those astral nets out. Because he is a primal of darkness."

I've tried to read up on the aether lore/system of FF14 and honestly I don't understand it?
I've read that Astral and Umbral are the "polarities" aether can have.
Is it correct that Astral is Light and Umbral is Darkness (umbra = shadow)?
So if the Astral flow = the Light flow is already weakened, why do you need to summon a primal of Darkness to balance it out? Should that not tip the imbalance even further away from the Astral polarity?


2. How are Ascians reborn?

We learn that the souls of unshattered Ascians go back into the lifestream, too.
Later we hear some characters talk about how they hope Emet-Selch and Hythlodaeus will be reborn sometime in the future (am I messing this up? I think that was stated, right?).

But how exactly would they be reborn? Just as Ascians? Or is that out of question now that their original world is gone?

(I don't know how rebirth works in FF14. Can any soul just be thrown back into the living world again, no matter the circumstances of the current world? Or is there some kind of sentience/controlled decision behind this?
E.g., the Ascians' civilisation is gone, the era of their people is over and their original world - the unsundered planet - doesn't exist anymore?
Or could it have anything to do with the planet's aether structure? The original unsundered planet, the Ascian habitat, had a completely different aether structure, so maybe there was some kind of "attraction" between the aether of the original planet and the Ascians' souls that pulled them back from the lifestream?)

I would theorise they can't be reborn as mortals, because the aether constellation and denseness of their soul is different from that of mortals/shattered Ascian souls, right?
(It's stated their presence contains a lot more aether (which hinders them from being taken over by Dynamis and only their magic of creation is affected) than that of mortal beings.)


3. So which "version" of time travel happened?

I know, time travel never really makes sense anyway but at least I want to understand in which way it doesn't make sense. :P

Is it the one-way time travel, which means that before we travel Venat/Hydaelin, Hermes, Emet-Selch and Hythlodaeus have never met the WoL and after I return I'm technically in a different future?
Or is it the loop time travel? So the time-travel already affects the original timeline to begin with, Hydaelin already knows everything and my time-travel is already pre-determined? (Kinda like the time turner in Harry Potter.)

I know, technically the game says our action could change the actions in the future (but not the events/outcomes) implying that originally none of it has taken place.

But then there's something I don't understand about the original time-line:

How did Hydaelin know the Elpis flowers are the key? Did she just somehow Find Out with her Goddess primal powers that Dynamis is the cause and remembered that Hermes had been researching Dynamis but she didn't know the details?


4. In the timeline altered by time-travel (no matter whether it's the new timeline or it has always been like this because of a loop) how did Amon actually get Fandaniel's memories back?

I know they try to explain it after the dungeon but it's still not entirely clear to me.
So Hermes has forgotten everything when he is the Fandaniel in the altered timeline because of the Kairos but he does not die, so his soul doesn't return to the lifestream and his memory loss shouldn't be reversed. He is however sundered. So the soul "shard" dies and is reborn which causes fragments of the memories to return.
And when he gets the crystal of Fandaniel everything finally comes back to him. I assume these Ascian crystals are similar to job crystals which can hold the memories of their previous owners?
But that crystal is from the Fandaniel who never had his memories re-established, e.g., by death so how can Amon get all these memories back in a time-line where time-travel/Kairos happened? Is it enough when a soul shard is reborn? Can that undo the Kairos effect in the Fandaniel Crystal's memory aether?

My assumption regarding the old time-line is that Fandaniel knew about Meteion's prediction and actions but purposefully kept the Convocation in the dark, just like Emet, Hythlo and Venat speculate when you are in Elpis. So the Amon of the original time-line should inherit a crystal whose memories are intact.