Roman Magic
All I can think of is that myth about Zeus. Transforming god that takes the form of farm animals. Gets close to mortals and then changes to his god-like form an has his way with the ladies. And now we have the source for magic in this world. All magic derives from the bloodlines of the gods. Thanks!
Perhaps the gods aren't gods, but ancients that had access to arcane knowledge that was lost during the Greek Dark Ages, but has been rediscovered at the eve of the Eastern/Western Roman division. Could be an interesting alternate history campaign.
And now I know that there was a Greek dark ages. I don't know how I didn't get that the Homeric era was literate and kept careful record but still had myths get created during it. Huh, again very interesting stuff thanks for the post!
Thanks! I'm a big fan of alt-history, and your suggestion got me thinking about the what-ifs.