(Bull of Heaven)
In Mesopotamian mythology, the Sky Bull is a legendary monster that was fought by the hero Gilgamesh. The story of the Sky Bull has two different versions.
[One recorded in an earlier Sumerian poem]
The second is in the famous Akkadian Epic of Gilgamesh.
In the Sumerian poem, the “bull” is sent to attack Gilgamesh by the goddess Inanna for unclear reasons.
While the Akkadian narrative becomes more complete in the sixth tablet (of the Epic of Gilgamesh), where Gilgamesh rejects the temptations and offers of the goddess Ishtar, which prompted her to ask her father (Anu)
By creating the Heavenly Bull to send it to attack Gilgamesh in Uruk.
[Anu] gave her the bull and sent it to attack Gilgamesh and his heroic companion (Enkidu), who killed the bull together. Then (Enkidu) cut off the right thigh of the heavenly bull.
He threw it in Ishtar's face, mocking her
The slaughter of the bull led to the pantheon of gods condemning Enkidu to “death,” and this stimulated Gilgamesh’s fear of death, pushing him in the remaining part of the epic to search for “immortality.”
Source: websites