What is Ascian prime? (Spoilers for Shadowbringers)

[Cilia]

I actually have to wonder if Emet's form in the trial isn't some "Super" Ascian Prime thing. It seemed to me like he fused with/was buffed by the spirits of ancient Amaurotines, given all the Ascian masks that appear in the background during the fight.

His first form is arguably the closest thing the Ascians have to a "true" form, given as they don't typically have physical forms that aren't stolen and remade in their image. (While Emet-Selch does take on the form of "Solus zos Galvus," it's rather unlikely that's his original form. Back when he was setting up Allag, he probably looked different.)

Hades' second form is using the souls of dead Ascians to further power himself up, though. Or so it's implied.