The Pantheon & the Divine Assembly
The gods govern as a council — and the world's fate is whatever they decide in session.
Also: pantheon · divine assembly · council of the gods · puhru · great gods · the Anunnaki
The Mesopotamian gods form a society, not a solitary deity. The great gods — An/Anu (sky), Enlil (the divine ruler), Enki/Ea (wisdom and the sweet waters), the moon Nanna/Sin, the sun Utu/Shamash, Inana/Ishtar — meet as an assembly (puhru) to deliberate and to fix destinies. Decisions are reached collectively and announced as decrees. This 'divine assembly' models the cosmos on a human city-council and is the setting in which floods are decreed, kings are chosen, and the world's order is debated.
In short
The organized community of the great gods, governed like a council or assembly that meets, deliberates, and decrees the fates of gods and humans.
Where it’s found
Pervasive; e.g. 'Enki and the world order' (ETCSL 1.1.3); the assembly decreeing the Flood in the Sumerian Flood story (ETCSL 1.7.4) and Atra-ḫasīs (akkadian-pending)
How the idea developed across Sumer, Babylon & Assyria
Sumerian texts make Enlil of Nippur the presiding power of the assembly; Babylonian theology gradually elevates Marduk, and Assyrian theology Aššur, to that chair. The roster and ranking shift over three millennia, but the council form is constant.