The Igigi are the minor deities of the Mesopotamian pantheon. Although they were not as powerful as the Annunaki, they were many. If they joined forces, they were powerful enough to make even Enlil worry.
Traditionally, they were tasked by the Annunaki to do the hard labor involved in shaping the world as we know it. Amongst others, they were commanded to dig the Euphrates and the Tigris. After rising up in rebellion, their labor was shifted to mankind.