Hear me out on this one, but feel free to rip it apart in the comments.

The "Eyes of 9" are a council of mages from aeor (like an evil cerberus assembly) that attempted to manipulate a source of magic maybe related to what the Luxon produces (time travelling? WMD?) and instead plunged Aeor into an extraplanar... place. From the city they are able to bestow the Nonagon with ancient magics (or the Nonagon was able to visit and be accepted as the savior and then empowered) in order to return the city to the primary material plane so that the mageocracy might regain control. Make Exandria the Age of Arcanuum again, sponsored by the City of Aeor and the Eyes of 9.

The method of empowerment/identity of the Nonagon is still a bit of a question mark; I am not sold on my own idea presented above. Chosen one? Messiah? Found an instructional book and figured out how to become it? Lucien/Molly's dialogue in E117 indicated that the tattoos, and thus the power, was gifted to him by the 9.

Vess DeRogna (potentially along with other members of the Assembly) was definitely interested in using artifacts (or magics) from the Age of Arcanuum to further empower herself/the C.A., maaaybe even to model themselves after the Eyes of 9. This is a very deep assumption that is just a guess, and might not be true due to their curiosity into the Luxon Beacons--why would they bother if they knew where to go to find the real stuff? Fun bonus--Delilah Briarwood was kicked off the C.A. before she appeared in C1 for necromantic practices; yeah, she was a necromancer, but technically wasn't Halas one too? She had the same role as Vess on the C.A., maybe she found out about Aeor and tried to get there too, but the Assembly found out and covered it up.