So, the major discovery is another civilization: Karnak! Karnak's named after the city from FFV that had the Fire Crystal, but what we have mostly suggests that they were roughly Mesopotamian in terms of aesthetic, with turbans and ziggurats. For what it's worth, when I combine 'FFV' and 'turbans' I land on Mystic Knight, who aren't currently present anywhere in the game. They were also a magical civilization, but interestingly, Archive at least in English places Karnak
outside of the 5AA's 'twelve city-states'. I wouldn't be confident about that without looking at other languages, though. The Occult Record seems to hint that Karnak worshipped Nald'thal, and more as a god of the forge than modern perceptions of 'the god of commerce'; more Hephaestus rather than Plutus.
Someone has actually suggested to me that 'the twelve city-states' might actually be a grouping more than a numbering, similar to Norse mythology's 'nine realms'; if you actually count the realms in Norse myth there's more than nine. In that case we might not actually be looking at a set-in-stone, concrete group of twelve.
As for the civilizations we already knew about, we don't get a lot of clear info, but of what we do have, Skalla's probably the biggest one: Treasure Tortoise of all sources confirms that they had 'mighty mages', but wasn't really specific beyond that. From there, I'd actually put forward that our best intel are the Phantom Jobs: so far, we have twelve.
- Knight
- Monk
- Thief
- Samurai
- Berserker
- Ranger
- Time Mage
- Chemist
- Geomancer
- Bard
- Oracle
- Cannoneer
I feel like it's probably fair to narrow Skalla's input on this down to the explicit magic jobs: Time Mage, Geomancer, Oracle, and maybe Chemist. Twelve jobs would reliably sync up to 'the twelve city-states' (if there were indeed twelve), but none of them explicitly sync up with anything we already know about the 5AA civs, so who can say.