In Mesopotamian mythology, Ereshkigal (lit. "great lady under earth") was the goddess of Irkalla, the land of the dead or underworld. Sometimes her name is given as Irkalla, similar to the way the name Hades was used in Greek mythology for both the underworld and its ruler.
Ereshkigal was the only one who could pass judgment and give laws in her kingdom. The main temple dedicated to her was located in Kutha
The goddess Ishtar refers to Ereshkigal as her older sister in the Sumerian hymn "The Descent of Inanna" (which was also in later Babylonian myth, also called "The Descent of Ishtar"). Inanna/Ishtar's trip and return to the underworld is the most familiar of the myths concerning Ereshkigal.
She is known chiefly through two myths, believed to symbolize the changing of the seasons, but perhaps also intended to illustrate certain doctrines developed dating back to the Mesopotamia period. Ereshkigal is therefore the sister of Ishtar and from one point of view her counterpart, the symbol of nature during the non-productive season of the year. As the doctrine of two kingdoms, one of this world and one of the world of the dead, becomes crystallized, the dominions of the two sisters are sharply differentiated from one another.
One of these myths is the famous story of Ishtar's descent to Irkalla or Aralu, as the netherworld was called, and her reception by her sister who presides over it; Ereshkigal traps her sister in her dark kingdom and Inanna/Ishtar is only able to leave it by sacrificing her husband Dumuzi in exchange for herself. The other myth is the story of Nergal, the plague god, whose offence against Ereshkigal, his banishment to the kingdom controlled by the goddess and the reconciliation between Nergal and Ereshkigal through the latter's offer to have Nergal share the honors of the rule over Irkalla. In later tradition, Nergal is said to have been the victor, taking her as wife and ruling the land himself.
It is theorized that the story of Ishtar's descent is told to illustrate the possibility of an escape from Irkalla, while the other myth is intended to reconcile the existence of two rulers of Irkalla: a goddess and a god. The addition of Nergal represents the harmonizing tendency to unite with Ereshkigal as the queen of the netherworld to the god who, in his character as god of war and of pestilence, conveys the living to Irkalla and thus becomes the one who presides over the dead.