Here some general observation, which for most part are not bad. I don't know much about the precise lore, so some may be logical with advanced lore knowledge.
* Kuriotates benefit from Fellowship of the leave far more than from any other religion. Guardian of nature essentially give infinite happiness, forest give usually more than enough health, and on top of that you can put cottage on forest, which mean that it's crazy on end game (4 food + 2 production + 6 gold ...) and pretty good on mid game.
* elven people tend to generate a lot of population because of ancient forest, which seem strange for elves, not a race usually associated with breeding like rabbit. Only Calabim and Kuriotate tend to generate even more population, while people like Grigori, Hippus, and co are usually far less populated.
* some thing would be far easier to understand with proper explanation on the sevopedia, like the Amurite and Kuriotate world spell, or how animal are selected with Call Animal
* Capital can be holy city even with other city, which I don't recall as being possible on vanilla Civ
* Call Animal can call an hawk. Usually it's just completely useless, and when you need an hawk you'd better build it than gamble for it (may be only on an "old" version).
* The Luchurip AI seem consistently more efficient than the other, most notably because she seem to be able to consistently copy all the promotion of Barnaxus on each and every golem. Since golem already are stronger than regular unit and Barnaxus tend to have more experience than random unit, it make them very hard to keep in check if you can't or don't want to assassinate Barnaxus as soon as possible. Other factor are possible, of course.
* on advanced start, civilisation with "special" starting unit like adept for Amurite don't get them. In the same way, if you discover first a religion, you get the holy city, the disciple, but not the priest unit. Not exactly something worth fixing
* the kuriotates have a nasty combo between creation spell I (Muse) and settlement in that you can use the only citizen of the settlement to be a merchant (with the slot provided by the Muse) which will be productive. It mean you can spam city to get gold per turn while keeping an handy reserve of adept.
* I believe having both level of creation mana being city-oriented and very powerful is too powerful. Adept are cheap, and reasonably quickly every city will get +10 food, +4 culture, and some specialist slot.
* ashen veil love the seemingly unnatural combo creation III + Sacrifice the weak, even if it is very costly. I haven't tired to see whether Lich can cast Creation III spell, but it seem not intended
* I have consistently seen the AI summon Basium, but never seen any Infernal player being created bu the AI. On the same idea, I have never seen the AC go over 25 if I wasn't actively trying to make it so. And in general, Evil civilisation tend to die and good civ tend to thrive. It may make philosophical sense, but it lessen tension. Admitely, I would like to see the AC going to at least 40 or 50 "naturally".
* The kuriotate Dragon put all other "uber" unit to shame, since it start with 15 more strength than the usual dragon and have all the utility promotion you need. However, you can't remove Crazed or Enraged from him with spell
* As Kuriotate, I have done Stir from Slumber while Auric had not killed any civilisation and Sheaim were not present at all. Drifa returned as a barbarian, while Abashi (that I was camping with 30 courage'd centaur) did not spawn.
* the Illians are artifically weakened as AI because they don't understand that Auric Ulvain is precious, so they suicide him on attacks. Not making it spawn or helding it in place may help.
* I have seen Malakim beating the Bannor by one turn to create Ashen Veil. I am not too sure what they were trying to do, especially since they did not propagate Ashen veil, create the holy building, or anything.
* I have seen multiple time the Sidar proposing me a deal for whale, then cancelling it the very next turn. Since I didn't care for the ressource, it was not problematic, but a bit strange.
* speaking of the Sidar, is there another use than obscuring again the map ? It seem very weak as world spell.
I hope that at least some of the feedback will be useful