The Revival team has posted a brand new developer diary to introduce fans to the importance of religion in the game when it arrives. Each city will have a pre-defined religion attached to it, but that religion could be altered over time.
A city chooses a temple for a god based on that city’s karmic alignment, player karmic alignment (players using or constantly congregating in/around the temple), and idol/altar influence. Idols and Altars are things players can purchase for their homes to facilitate worship of the deity of their choosing. This means that players can collectively all worship a new type of god in their homes within a city and have significant impact on the city’s religion.
Read the full post on the Revival site.