fabulous, mythic, mythical, mythologic, mythological
Meaning: based on or told of in traditional stories; lacking factual basis or historical validity; "mythical centaurs"; "the fabulous unicorn"
As has been indicated, a mythological system must have been strongly influenced by city politics.
In dealing with the city cults of Sumer and Akkad, consideration must be given to the problems involved by the rival mythological systems. Pantheons not only varied in detail, but were presided over by different supreme gods.