Where do the Ascian black masks come from?
By which I don't mean the Ascians themselves. I mean the black masks they wear.
Based on pre-Shadowbringers knowledge, we know that the Ascians wearing red masks are the powerful ones, whether Sundered or Unsundered. The black masks, in comparison, are pretty much minion-level: the Ascians of the Twelfth Chalice are "lesser Paragons" and allegedly under the command of Lahabrea, and we explodify them during the level 60 SMN quest. And during the ARR Hard and Extreme Primals, a few black-masked Ascians also show up mysteriously, say some mysterious comments, then mysteriously disappear.
Much later in 5.3, during the big brouhaha about Elidibus minting new Warriors Of Light, the Scions also mentioned a proliferation of black-masked Ascians, which Urianger reminds us are "of inferior rank" to the red-masked ones. These are handled offscreen, by both the new Crystarium Warriors Of Light, and presumably any Scion who happened to be there.
So the idea is that Ascians wearing black masks are servants and less powerful to the Ascians wearing red masks.
Except when we look around Emet-Selch's recreation of Amaurot, and later go ourselves into Elpis, there are no Ancients wearing black masks. Everyone, except for current Convocation members, are wearing white masks.
It's not even that only the subordinates of the Convocation wear black masks: in Pandemonium, Erichthonios and Hesperos have white masks. (Well, Hesperos wears a white mask in flashback, and when he actually shows up in front of us in his Dracula cosplay, he has no mask at all.)
Where did this tradition of "lesser" Ascians wearing black masks come from? Why did the Ascian Overlords not give them white masks?