This is a bit of a weird tangent, but...
This got my gears turning, and I went and looked up the Sagittarius Lucavi to make sure I remembered who it was and what she was known for. Sure enough, it's Shemhazai, the Whisperer/the Betrayer (English/Japanese titles respectively). The clan primer bio for her from FFXII has this to say:
And having refreshed my memory on this, I can't help but notice some odd parallels between her and Hydaelyn and Minfilia. Hydaelyn, existing at the heart of the aetherial sea, is as close to controlling the souls of the underworld as anything in XIV can hope to be. And like Minfilia, Shemhazai both served as guardian for her patron gods and later on acted as an oracle. But whereas Minfilia parted with Hydaelyn on good terms and was acting in her stead, Shemhazai betrayed her masters and acted against them. Also of interest is the Scion of Light she was created in opposition to—Igeyorhm, who 5.3 elevated above the rest of the Sundered Ascians to some extent.Scion that is both horse and woman, wielding utter control over the souls that wander the underworld, in opposition to the Martyr Igeyorhm, scion of light. Though she once served the gods as a guardian, when Ultima announced her rebellion, Shemhazai went to her, whispering of the gods' hidden weaknesses. She then descended upon the land without leave of the gods, and taught men of destruction and evil. For this was she stricken down and bound.
Again, all of this is a very weird tangent, and none of it has anything to do with what we might be doing come 6.0. It's just cork board conspiracy theorizing, really. But if it's not absolute rubbish, I can't help but wonder now if the mysterious "fairy" behind Gaia's powers is actually Igeyorhm. Aside from certain hard facts—namely that we killed her in an apparently permanent fashion—she potentially fits the bill a bit more than the Ascian I expected it to be. Would be hell trying to explain how she "survived" us, though. Death is but a door, and time a window, I guess?
Gods, I wonder if we'll actually see Shemhazai in a later addition to Bozja. That'd be swell.