The clones of Emet.

[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.