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.
The duty of the gods is to maintain the world and man’s place in it, and prevent it from being consumed by the lingering forces of chaos (Tiamat). The duty of humans is to faithfully worship the gods, and (directly and indirectly) aid the gods in maintaining what is just and good in the world.
Priests of the Church serve through academic knowledge and proselytizing (guiding the flock). The martial arm of the Church, the Cleric orders, serve to uphold the law as well as push back the forces of chaos. In the Eastern Empire, justices and sheriffs are branches of the clerical order, and serve to bring law to the lands of men. Priests and Clerics can perform miracles…this is not, by definition, magic.
As per the Code of Hammurabi (the codified law of mankind as dictated by Marduk), there are three classes of man. There are Noblemen (who own land), Freemen (who may purchase land), and Landsmen (who are owned in conjunction with a defined piece of land). In the west, landsmen are known as serfs. In the East, the noblemen are known as the Amelu, the Freemen are known as Mushkenu, and the Landsmen known as the Ardu. While the Code of Hammurabi assigns different protections and punishments for men and women, both genders are represented in all three social classes.
The thronging demon hordes that lie outside time and space, awaiting the slightest opportunity to enter the world and despoil it are of Chaos. The great Demon Lords of the Abyss, descendants of Tiamat, are their leaders. The magic that human sorcerers and wizards employ is of chaos, although not all such practitioners seek to serve the cause of Chaos directly. Still, they are viewed with suspicion by the Church and the clerical orders (some of which are specifically tasked with destroying cultists of Chaos, magic using or no).
The Fair-Folk (elves, dwarves, halflings) predate the arrival of humanity in the west. Although their races are in decline (or absent altogether in some regions), their own worship of elemental and inhuman forces (the Old Gods) continues on. The Dagda, Morrigan, Lugh, Brigid, and Manannán, are all still worshiped by the Elves, and continue to grant their favors to their worshipers. The Old Gods have no church, and the miracles they grant their followers are of nature, and of balance. Their priests are known as Druids.