The clones of Emet.

[Cleretic]

Lahabrea specifically was hoovered by the eye, but the eye itself was transmuted into Shinryu. Once Shinryu was destroyed, I'm not sure what happens to that aether- the body is destroyed, but the actual Aether...what happens to it? Are the "Lahabrea" nanoparticles released and able to recombine?

We also don't know if Elidibus is dead, as he was merely sucked into the Crystal Tower.

Additionally, we are not 100% sure that they even actually are dead-dead once they rejoin the lifestream. No ascian has ever been killed until this specific era, so we assume they are dead because we haven't heard from them, but for all we know they might need a larger amount of time to reform.

Okay, so in order:

Remember that the eye didn't just power Shinryu; before that, it also powered Nidhogg-Estinien, and before that, the Knights Twelve. After Shinryu is destroyed, both eyes are then destroyed by Estinien-Estinien. We then later see him tapping into the power of Nidhogg, although it's nebulous as to how. So Lahabrea got sucked into a battery that was then tapped into for two separate huge efforts, and then was either totally destroyed or is still being tapped into somehow. I think it's unlikely that Lahabrea remained intact for all too long there.

For Elidibus... well, we hit a similar problem as with Lahabrea before factoring in the consumptions. Like Lahabrea, he's in a battery; there's actually an unresolved question there as to whether or not a soul absorbed in that context is even intact, or if it's basically just converted into raw, order-irrelevant energy. Electricity generated from solar power doesn't remember it came from the sun; we don't know if the same logic applies to souls sucked into aether batteries. But I assume we'll be able to ask Lahabrea in a few months.

And we actually do know what happens when an Ascian rejoins the lifestream, because remember: Eden. Loghrif's soul was in the First's lifestream for... eighty-some years, let's say, since she died a hundred years ago in the First's timeline and Gaia is somewhere in her mid-to-late teens now. However, when she returned, it was without memories; Mitron went on to mess with her brain even further, but the scene right after E12 makes it clear that they reincarnate without memories anyway, and they generally seem to expect Mitron will get spat back out, sans memories, sometime after Gaia has passed.

I would actually think that the only Ascian incapable of reincarnating, at least in the natural process, is Emmerololth; being ripped apart by the Lifestream itself, she's unlikely to get put back together by it.

[kaynide]

…

All a valid interpretation, but it’s not necessarily set fact.

Like electricity, it’s pretty clear Aether does not become lost upon use, it just merely changes form.

Rather than just becoming converted to kinetic energy or heat, generic aether rejoins the life stream to be reformed into new life.

The big question mark for me is if there is a difference between generic aether and Ascian aether, especially since their aether specifically can stay together to be reborn. It stands to reason that even Lahabrea’s released aether could reconstitute given enough time.

The only certainty I can gather is that the unsundered have not been slain before this point, so even if they can return, they are unaware of it.

Were this real world, as a scion or WoL I would push to research this heavily, but again as a game…probably we can trust they are dead until the story needs it to be otherwise. Especially given Emet and Elidabus’s fair well moments.

[MikkoAkure]

All a valid interpretation, but it’s not necessarily set fact.

Like electricity, it’s pretty clear Aether does not become lost upon use, it just merely changes form.

Rather than just becoming converted to kinetic energy or heat, generic aether rejoins the life stream to be reformed into new life.

The big question mark for me is if there is a difference between generic aether and Ascian aether, especially since their aether specifically can stay together to be reborn. It stands to reason that even Lahabrea’s released aether could reconstitute given enough time.

The only certainty I can gather is that the unsundered have not been slain before this point, so even if they can return, they are unaware of it.

Were this real world, as a scion or WoL I would push to research this heavily, but again as a game…probably we can trust they are dead until the story needs it to be otherwise. Especially given Emet and Elidabus’s fair well moments.

I think the implication was that while they're whole and sentient, they can avoid being sent to the lifestream and are free to go and possess another random person when something happens to them. The lore book stated that was due to a "crystal of darkness" which is probably just their connection with Zodiark. In order to get rid of them permanently, they need to have their aether pinned down so they can't leave, and then get blasted with a high dose of aether. I think at that point, they have no conscious ability to maintain their form and their consciousness gets scattered into the ambient aether/lifestream of the world.

Emet-Selch/Hades was a master of the Underworld/Lifestream when he was alive so that could explain his shenanigans during the fight with Elidibus. But he also seemed to be content to help us instead of moving the ascian plan forward and went quietly into the night. That being said, he did voice the Endwalker trailer so I wonder if there will be more of him or if his narration was just supposed to be a parallel to his speech to us in Amaurot about the Final Days.

[Cleretic]

I think the implication was that while they're whole and sentient, they can avoid being sent to the lifestream and are free to go and possess another random person when something happens to them. The lore book stated that was due to a "crystal of darkness" which is probably just their connection with Zodiark. In order to get rid of them permanently, they need to have their aether pinned down so they can't leave, and then get blasted with a high dose of aether. I think at that point, they have no conscious ability to maintain their form and their consciousness gets scattered into the ambient aether/lifestream of the world.

Emet-Selch/Hades was a master of the Underworld/Lifestream when he was alive so that could explain his shenanigans during the fight with Elidibus. But he also seemed to be content to help us instead of moving the ascian plan forward and went quietly into the night. That being said, he did voice the Endwalker trailer so I wonder if there will be more of him or if his narration was just supposed to be a parallel to his speech to us in Amaurot about the Final Days.

No, we actually saw the crystals of darkness, more than once. Immediately, I remember that Igeyorhm called hers up and was about to use it before we White Auracite'd her and then lasered her with one of the Eyes of Nidhogg.

They are a literal, physical thing, we're just thorough enough to rarely see them.