The Epic of Gilgamesh is a story that was created by ancient sumerians. Gilgamesh was a 2/3 god that was given a challenge to find and achieve immortality. The story is about a king (Gilgamesh) in the city of Uruk that tyrannically abuses everyone without any empathy. The people of the city cry out to the gods for help so they can relive their lives. The gods hear the peoples struggle and create a man named Enkidu to help Gilgamesh find his immortality. The meet up in Uruk and become companions. Enkidu tells Gilgamesh of a monster that lives in the Cedar forest that must be defeated. After their victory, Enkidu has a dream that the gods have a meeting of choosing a hero to sacrifice. Enkidu is given a sickness and eventually dies. Gilgamesh is torn to see death and decides to find immortality. He sets off to find Utnapishtim which will grant him immortality. He finds Urshanabi to ferry him across the waters of death. When arriving on the shore, Gilgamesh approaches an old man that tells him that immortality is for gods alone. Gilgamesh then returns home to Uruk. Utnapishtim hears of him and tells him to find a magical plant at the bottom of the sea that will restore one's youth. During his return, he left the plant unsupervised and a serpent took it. He returned home only with the understanding of the importance of life. The city of Uruk now looks at him as a king.
Here is Gilgamesh and Enkidu slaying Humbaba.