We consider a formal model of polytheistic religion, where worshippers choose gods to address, and expect benefits in return. At the game-theoretic equilibrium, they choose gods optimally depending on how the gods return favors, as a function of divine efficiency. This efficiency can be modeled based on a random growth model of prayer benefit, and results in worship acts following power laws. A reduction in the range of random events associated to the various divinities, or to their range of interpretations, leads to more concentration of worship towards less divinities.