This question is inspired by a popular medieval fantasy trope (that is not, in any way, ASB, despite it appearing so much) in which the primary or one of the primary settings is a kingdom with pseudo-christian, or maybe just uniquely inspired medieval ethics, with an organized clergy preaching a polytheistic or "aspect-based" monotheistic religion that is at least a little proselyte, if not as vehemently as Abraham. Part of this can obviously be chalked up to historical illiteracy, but it some of the more well thought out stuff gets me thinking- is it possible? Can there be a truly polytheistic, nonsyncretic religion in history that is proselyte? Please do not mention Hittite religion (despite how cool it is), it may be antisyncretic but that's because they went with . . . oh I don't know how to say it, omnilatry instead of syncretism.