The Jailers of Al'taieu are certainly interesting.
Chains of Promathia is ultimately a tail of faith and of the true origins of Vana'diel and its deities.
Remember though, where Al'taieu was before it was cloven from Vana'diel and moved to Lumoria.
It was the Zilart capital, and it was an island that lay in the Sea of Shu'Meyo. This is the sea that surrounds Qufim Island. Now it could have been part of Qufim Island at one time, as Qufim Island is a nearly perfect crescent, but that would be pure speculation as nothing states that directly.
Either way, when it was cloven from the land, it was cloven from the sea itself as well. Not just the Zilart were taken to Lumoria along with it. The animals surrounding the palace and surrounding its island were also taken along.
Also note that like Sky, there are invisible or what were supposed to be invisible barriers for people to walk upon. Unlike Sky, these seem to have come into play due to the land being cloven. It's a forcefield to protect the palace. It generated a field over the water flooding the island that was brought along, and it surrounds Lumoria in the sky, and that's why the entire sky of sea is lavender and grey hexagons.
Even further you will note that the forcefield you walk upon in Sea is several meters higher than the actual ground, and infrastructure that would normally lead up to the palace doors is actually damaged. Even more, there are plants that are completely submerged that show no signs of damage or being different than anything else in the area.
However, all plants and the ground have turned varying shades of blue, teal, purple, lavender, and white. Seemingly, oddly, temporally frozen and unaffected save their colors by the events around them. And the Quasilumins confirm that time doesn't seem to be or feel the same in Lumoria. There is no night or day. They know tons of time has passed because there used to be people, and the place used to be a, "beautiful garden." Many quasilumins on the outside refer to missing or serving their master, and say they are not permitted inside the palace. One also says that there are entities killing anything biological within the palace.
This reflects the true state of things. Yve'noile sealed the King of the Zilart who'd become Promathia's vessel in the throne room. She used the light of her life force to do that, and went comatose in the Chamber of Eventide, a final bulwark from its accumulated darkness/Emptiness spilling forth.
Those entities that kill biological beings are the Luminions, not quite arcana that have been made at an indeterminate time within Al'taieu's residence in Lumoria. Z'deis and Ghrahs. They don't show any hostility towards Aerns or Euvhis, however.
These are extra guards against anyone getting to the throne room, to interfere with Yve'noile's seal. Their purpose repurposed, possibly by Selhteus, but possibly by the Zilart themselves before they lost their bodies (and some of them their minds).
This brings into question what a Luminian is, the biological beings that do reside in Al'taieu, mostly outside of the palace. We have Aerns, Xzomits, Phuabos, Hpemdes, Euvhis, and Yovras. Most of these resemble transmogrified animals/plants. Xzomits are squids. Phuabos are sharks. Hpemdes are dolphins (no they're not goldfish). Aerns are humanoid. Euvhis are flowers.
Yovras are freakishly alien. They have tentacles numbering up to 12, and 4 of which are hidden in their stem. They to me, seem to be something of XI's take on biblically accurate angels.
These Luminians all seem to be possessed of immortality, shown by their organ descriptions. "Though you've cut the organ away from the body, it still functions."
We can infer that mostly these were what became of the animals that came along with Al'taieu across dimensions. We can also infer that the Aerns are the other Zilart or Kuluu who did not become Quasilumins.
In order to fight Absolute Virtue and the other sea Jailers, you have to start by getting the Deeds from the Ix'Aerns. These Deeds and the oncoming Virtues from the jailers are memories suspended in a physical bubble that coalesced after you killed them.
Lumoria is pushing in on the boundary between Vana'diel and the realm of the gods, so it would seem that certain beings that came along with Al'taieu now transcend mortality.
We're missing the 10000 year interim, and we don't actually have a precise time for when Promathia manifested in the King of the Zilart. But it stands to reason that since memories and souls are at play, and you can carry them in your inventory, that it may have been some other deities also began to manifest in the Luminians, like Promathia did in the Zilart King.
Further still, if this happened while the King was still The King, perhaps he ordered them to be sealed away as best he could. Just like in Sky with Kirin, to access the later Jailers, you ascend through a path of Luminions (the Arcana) and Aerns (loyal humanoids) in order to fight godly beasts.
AV's dialogue on claim reveals that these virtues and memories held by all of the Ix'Aerns and Jailers were his. Like with Kirin, he was sealed, and we broke the seal to kill him in the name of treasure. In this case, they are AV's memories of his sins.
They become physical, and you give them to Meret, the other researcher near Yurm the gorget/obi lady, to receive the items.
It's a mystery even for our NPCs.