[Coldsaturn]

Here I go with more details after rewatching. Spoilers will be hidden.

- Can we just take a moment to appreciate how this whole thing looks like Final Fantasy and DarkSouls were blended together, and Xavier looks what a three way pregnancy between Cloud, Noctis, and Sephiroth would look like if it was possible.

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"For centuries it's as if I've been in a long dream...Until that light led me out of centuries of darkness and solitude."
This is very cryptic. I can't tell whether this is referencing MC or Xav. Possibly both. Them being fated soulmates and all, they'll mirror each other in this. And since Philosian people are immortal, talking of centuries is no biggie.
BUT. It could also mean this takes place after Xav's standard myth. Which would change his character's lore a lot because up until now Xav has been the only LI who is not a reincarnation of himself, but is actually the very same dude from his myth. If we jump ahead to this future possibility, we'll be officially introducing Xav to the concept of the multiverse. 
The other option is that this is still part of his backstory, and his failed time travel with TracebackII happens after this myth. Which doesn't seem to be the case, because it looks like they both die at the end?

- Those enemies, if they're wanderers, don't really look like the wanderers we've dealt with up to now. There are a few bosses who look like armored big bad guys, very human in how they move. This looks a bit like that.

- I can't tell whether Xav's horse has armor that makes it look like a unicorn or if it's an actual unicorn.

- "The Dead are trapped in a perpetual cycle...Only painful deaths await them."
This means that if you kill them they'll just come back again and then you kill them again and they come back etc.?

- "Leave while you still can or you'll meet the same fate"
Leaving is an option?

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"Xavier I curse you..."
WHO IS TALKING. This is entirely new. Either it's only relevant to this myth exclusively, or we're introducing a piece of info that hasn't come up with Xav until now.

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"Faith built on lies"
Coherent to what we know about Philos and its societal structure. The people don't know that they're being sent to die to feed the planet, and no one outside the royal family knows that MC is supposed to be the eternal battery.

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"The king and queen's sword cleaves through the conspiracy of "eternity"
Because "eternity" is actually a lie? Because what they're getting is feeding an artificial planet and becoming wanderers in the process, so that immortality is actually a conspiracy?

- MC bonking Xav in the head with the wooden sword. Adorable.

- The cinematic transition of them on the hill surrounded by flowers and then it flips into a battle field: chef's kiss.

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"Through immortality and oblivion, my path leads to your light"
I was reading somewhere (tumblr? reddit? twitter?) that the title in chinese explicitly mentions Samsara, which is a philosophical concept strongly present in the LaDS narrative, which speaks of eternal cycles through deaths and rebirths, going through oblivion to forget everything between one cycle and the next. We'll talk more about it once you'll be done with all the characters' lore, because they've been associated with the main realms of samsara (of where you can end up reincarnating), and this myth seems to point at one, too.