>>96364684
>How to best handle a conflict between a polytheistic and a monotheistic religion in a setting, in which polytheistic gods either objectively exist, or their followers clearly have god-given magic powers?
Just treat it like how it was back in the day where if the two peoples came into conflict their gods would also fight each other which I bet is why the armies of Constantine and the like kicked so much ass vs the pagans. Or just say the gods don't get involved with petty conflicts or whatever.
>What is the incentive to convert to the monotheistic religion?
That depends on the religion in question really since Christianity, Islam, the borderline monotheism of Isis worshipping Ptolemaic Egypt and the religions of the steppe had different paths.