The narrative begins before anything is named. Apsu, the fresh water, and Tiamat, the salt sea, mingle, and successive generations of gods are born from them. The young gods are noisy; Apsu resolves to destroy them and is killed first by the clever Ea. Tiamat, roused to vengeance, produces an army of monsters and appoints her consort Kingu as its commander, giving him the Tablet of Destinies.
The assembled gods cannot face her. Marduk, Ea's son, offers to fight on one condition: that if he wins, his word shall fix destinies and he shall rule permanently. They agree. He kills Tiamat with an arrow through her open mouth into her belly, splits her body like a shellfish, and makes the sky from one half and the earth from the other, setting her waters to be held back by bolts and guards. He arranges the stars and the calendar, and from the blood of the executed Kingu, Ea fashions humanity, whose defined purpose is to do the gods' labour so that the gods can rest.
The gods then build Babylon and its temple Esagila as Marduk's residence, and the last portion of the poem, much of tablet 6 and all of tablet 7, is a recitation of Marduk's fifty names, each with a short explanation drawing out its significance. Modern readers usually find this an anticlimax and skip it. It is in fact the point. The fifty names absorb the titles and functions of other gods into Marduk, so that the list is a theological instrument for subordinating an entire pantheon to one city's deity, and the battle narrative is the story told to justify it.