These deities formed a core pantheon; there were additionally hundreds of minor ones. Sumerian gods could thus have associations with different cities, and their religious importance often waxed and waned with those cities' political power. The gods were said to have created human beings from clay for the purpose of serving them. The temples organized the mass labour projects needed for irrigation agriculture. Citizens had a labor duty to the temple, though they could avoid it by a payment of silver.
What did the religious importance of city gods wax and wan with?
those cities' political power