Nergal was a Mesopotamian god worshiped through all periods of Mesopotamian history, from Early Dynastic to Neo-Babylonian times, with a few attestations indicating that his cult survived into the period of Achaemenid domination. He was primarily associated with war, death, and disease, and has been described as the "god of inflicted death". He reigned over Kur, the Mesopotamian underworld, depending on the myth either on behalf of his parents Enlil and Ninlil, or in later periods as a result of his marriage with the goddess Ereshkigal. Originally either Mammitum, a goddess possibly connected to frost, or Laṣ, sometimes assumed to be a minor medicine goddess, were regarded as his wife, though other traditions existed, too.

Erra is an Akkadian plague god known from an 'epos' of the eighth century BCE. Erra is the god of mayhem and pestilence who is responsible for periods of political confusion. He was assimilated to Nergal at some point.