A Dark Thought on Amaurot

[Cilia]

It seems pretty clear and cut that what attacked them was some form of extra terrestrial.

It's neither clear nor cut; the idea that a malevolent extraterrestrial entity is responsible for the Final Days is just headcanon, no more confirmed to be true than the idea that the Final Days were the planet itself punishing the Ancients for their hubris. We don't know if it's one or the other, or something else entirely.

On topic... we do know Amaurot excommunicated and struck from history those who violated their laws and regulations based on Azem being stricken from history. That said few among them supposedly had the "soul sight" that enabled the observation of specific soul hues; only Emet-Selch / Hades is known to have possessed that ability, though it's implied Hythlodaeus may have had it as well (and Zenos inherited it either way).

Ultimately we don't know what caused the Final Days, and that's one of the big mysteries we need to unravel in Endwalker.