Before the world was created, there was raw, formless chaos. The god Marduk killed the mother goddess Tiamat and used half her body to create the earth, and the other half to create both the paradise of šamû and the netherworld of irṣitu. There are many, many lesser deities in the pantheon of gods, but they are all the same gods regardless of where on the world you journey amongst human lands. The most popular are Marduk, Anu, Enlil, Ea, and Inanna.
As mentioned previously, there are many gods in the Pantheon. Some say more than a thousand. The forces Of Law, the Holy Empire, and the fighting brotherhoods (and sisterhoods) of clerics serve them all. They do not, perhaps, serve them all equally. But as the gods themselves are not equal, this should hardly be surprising. And so, to recap:
Known as Mithras in the western expanse of the Holy Empire, Marduk was the patron of Babylon, and Rome after it (as Mithras). With the shifting centers of power in the Empire (most recently to Byzantium), Marduk is no longer preeminent, merely eminent. Marduk is associated with the planet Jupiter, warfare, and justice.
Anu is the supreme sky god; associated with order, and the source of authority for the kings of men. Anu is the patron of the amelu (nobility) caste of imperial citizens, who aspire to his power.
A son of Anu, Enlil is associated with the air, earth, wind, and storms. Enlil was the patron of agriculture, and of the cities of Nippur and Assur. Enlil is the patron of the ardu (landsmen) caste of imperial citizens, who see him as a benevolent father figure for humanity.
A son of Anu, Ea is associated with fresh water, knowledge, mischief, crafts, and creation. Ea is the patron of the mushkenu (freemen) caste of humanity, who are inspired by his works. Ea is associated with the planet Mercury, and the city of Eridu.
Known as “the Queen of Heaven”, Inanna was associated with love, beauty, sex, desire and fertility. Associated with the planet Venus, her center of power was the city of Uruk (before moving to Parais, in the west).