That's going to be 72 if each civ has access to two minor gods at each age.
As simple as 9 * 2 * 2 * 2 = 72.
A whole lot of cultures and a variety of distinctions between them:
Huge difference : between a culture and another one (egyptians and norse for instance).
Big difference : between two different major gods of the same culture (Loki and Thor for instance).
(With further differences according to the choices of the minor gods which might be all different or not)
Also big : Same culture and same major god, but 3 distinct minor gods.
Not so big : Same culture, same major god and 1 out of 3 same minor god.
Quite small : same culture, same major god and 2 out of 3 same minor gods.
I plan to try all 72 combinations, but I don't know if I'll live long enough...
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À l'attaque!