What is Ascian prime? (Spoilers for Shadowbringers)

[Absimiliard]

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

Note that Emet-Selch claims to be stifled by his vessel of flesh right before impaling himself and initiating the second phase. The implication there is that his power was being restrained, seemingly significantly, by the host body he was inhabiting. Another thing I would point out is that his second form increases in size just after his mentioning of being raised up by the prayers of his fallen brethren. It seems more like he's emulating a primal by drawing strength from the prayers of the Ancients sleeping within Zodiark to further augment the already impressive might of his true aetherial (see: hostless) self. Could be both though.

What makes it difficult for me to believe he took in a bunch of Ascian souls is their imprisonment within Zodiark. With Zodiark split, one would think those souls quite well beyond his reach for the time being.