A (Highly Theoretical) Look at the Cycle of the Eras

[Cilia]

This again? For the love of...

Not gonna spoiler tag because while the thread itself doesn't say spoilers, the very first post says 3.2 spoilers.

Lahabrea is, more than likely, gone and dead forever. If you'll remember Minfilia and Urianger's lecture on the exact nature of the Ascians' immortality, they have the Echo and use it to drift between bodies. In essence, they are able to retain consciousness even without a physical form. However, this isn't what affords them their vaunted immortality. No, that would be their Dark Crystals, which they use to flee upon defeat. If you look at the choker Thancred is wearing while possessed by Lahabrea, it contains a white crystal on it - Lahabrea's Dark Crystal, which shatters upon his defeat in the Praetorium. Igeyorhm tries to use the same type of Dark Crystal before we chuck the Auracite at her, giving us the opportunity to off her with the Eye.

Lahabrea, on the other hand, is now customarily smug that he will live to see another day and no longer seems intent on fleeing. Enter Pope Thordan, who goes super and then offs Lahabrea. At no point does he make an attempt to use his Dark Crystal and flee; he's too shocked and incredulous to believe he could have been outplayed. King Thordan then consumes his aether in the same manner that Leviathan consumed the Sahagin Elder, which is a method of killing someone with the Echo. Assuming the Eye absorbed it instead, King Thordan would almost certainly have isolated Lahabrea's aether and burned it first, not to mention it having much left at all after Ultimate End seems unlikely. Regardless, if someone's blasted into raw aether, they aren't going to pull themselves back together, Ascian or not, especially if they got eaten by a Primal.

That is what the Dark Crystals are for - to give the Ascians an exit strategy in case things go south and they are in a vulnerable position.

The Echo alone doesn't grant immortality. Just look at the Sahagin Elder or all of the Students of Baldesion (save Krile).

I know some people want Lahabrea to still be alive in there because they like him as a character or want to personally off him, but... he's gone. Until we get hints he isn't, given the story presents him as dead and he didn't use the Ascians' exit strategy (Dark Crystal), he is dead.

As for the masked figure in 3.2's ending, my money's on Ilberd. But that's just my best guess, going on zero information to make a deduction with.