Sumerian religion was pantheistic in nature, meaning that it involved the worship of a great number of gods. All of them looked like humans but had superhuman characteristics. The gods were considered to be human in certain respects: they lived in a house (the temple), ate food (provided by sacrifices), married human women (the temple priestesses), and had children by them.
However, the gods were also immortal and had magical powers over the lives of their worshipers. In particular, they could deliver success in battle and at harvest time.
The Sumerians believed in four major gods of creation, each responsible for a different aspect of the universe. Anu, god of the heavens, had his main temple in Uruk. Ki was the goddess of earth, while Enlil, the god of air, wind, and rain, controlled prosperity and adversity and personified the floods that could bring both fertility and destruction. Enlil’s temple, the most important in Sumer, was found at Nippur. Enki was the god of the deep waters and also the god of wisdom who brought knowledge of crafts and writing. His temple was the Apsu at Eridu, and he was said to have created the earth and the people from the clay of the Apsu.
Below these four principle gods were three lesser deities. Nanna, the moon god, was father of the other two— Utu, the sun god, and Inanna, the goddess of heaven, love, procreation, and war. Every city had one of these gods as its patron, and a temple was dedicated to that god. Temple ceremonies, including sacrifices, were held daily. There were also innumerable other deities, including gods associated with specific mountains, plains, and rivers. There were even gods for individual tools like plows and axes.