Tablet of Ishtar, Inanna, Tammuz, Dumuzi

Ishtar was the goddess of love, war, fertility, and sexuality. Ishtar was the daughter of Anu.

Ereshkigal 

 She was particularly worshipped in northern Mesopotamia, at the Assyrian cities of Nineveh, Ashur and Arbela (Erbil). Besides the lions on her gate, her symbol is an eight-pointed star. Ishtar holding her symbol, Louvre Museum One type of depiction of Ishtar/Inanna The lion was her symbol (detail of the Ishtar Gate) In the Babylonian pantheon, she "was the divine personification of the planet Venus".

Ishtar had many lovers; however, as Gilgamesh noted, "Woe to him whom Ishtar had honoured! The fickle goddess treated her passing lovers cruelly, and the unhappy wretches usually paid dearly for the favours heaped on them." Animals, enslaved by love, lost their native vigour: they fell into traps laid by men or were domesticated by them.

"Thou has loved the lion, mighty in strength," says the hero Gilgamesh to Ishtar, "and thou hast dug for him seven and seven pits! Thou hast loved the steed, proud in battle, and destined him for the halter, the goad and the whip." Even for the gods Ishtar's love was fatal. In her youth the goddess had loved Tammuz, god of the harvest, and—if one is to believe Gilgamesh — this love caused the death of Tammuz.

Her cult may have involved sacred prostitution, though this is debatable. One of the most famous myths about Ishtar describes her descent to the underworld. In this myth, Ishtar approaches the gates of the underworld and demands that the gatekeeper open them:

Ishtar

 If thou openest not the gate to let me enter, I will break the door, I will wrench the lock, I will smash the door-posts, I will force the doors. I will bring up the dead to eat the living. And the dead will outnumber the living.

The gatekeeper hurried to tell Ereshkigal, the Queen of the Underworld. Ereshkigal told the gatekeeper to let Ishtar enter, but "according to the ancient decree". The gatekeeper let Ishtar into the underworld, opening one gate at a time. At each gate, Ishtar had to shed one article of clothing. When she finally passed the seventh gate, she was naked.

In rage, Ishtar threw herself at Ereshkigal, but Ereshkigal ordered her servant Namtar to imprison Ishtar and unleash sixty diseases against her. After Ishtar descended to the underworld, all sexual activity ceased on earth. The god Papsukal reported the situation to Ea, the king of the gods.

Ea created an intersex being called Asu-shu-namir and sent it to Ereshkigal, telling it to invoke "the name of the great gods" against her and to ask for the bag containing the waters of life. Ereshkigal was enraged when she heard Asu-shu-namir's demand, but she had to give it the water of life. Asu-shu-namir sprinkled Ishtar with this water, reviving her.

Then, Ishtar passed back through the seven gates, getting one article of clothing back at each gate, and was fully clothed as she exited the last gate.

Inanna

 Here there is a break in the text of the myth, which resumes with the following lines: If she (Ishtar) will not grant thee her release, To Tammuz, the lover of her youth, Pour out pure waters, pour out fine oil; With a festival garment deck him that he may play on the flute of lapis lazuli, That the votaries may cheer his liver.

[his spirit] Belili [sister of Tammuz] had gathered the treasure, With precious stones filled her bosom. When Belili heard the lament of her brother, she dropped her treasure, She scattered the precious stones before her, "Oh, my only brother, do not let me perish! On the day when Tammuz plays for me on the flute of lapis lazuli, playing it for me with the porphyry ring. Together with him, play ye for me, ye weepers and lamenting women! That the dead may rise up and inhale the incense."

Formerly, scholars believed that the myth of Ishtar's descent took place after the death of Ishtar's lover, Tammuz: they thought Ishtar had gone to the underworld to rescue Tammuz. However, the discovery of a corresponding about Inanna, the Sumerian counterpart of Ishtar, has thrown some light on the myth of Ishtar's descent, including its somewhat enigmatic ending lines.

According to the Inanna myth, Inanna can only return from the underworld if she sends someone back in her place. Demons go with her to make sure she sends someone back.

Dumuzi/Tammuz and Inanna. 

 However, each time Inanna runs into someone, she finds him to be a friend and lets him go free.

When she finally reaches her home, she finds her husband Dumuzi  (Babylonian Tammuz) seated on his throne, not mourning her at all. In anger, Inanna has the demons take Dumuzi back to the underworld as her replacement. Dumuzi's sister Geshtinanna is grief-stricken and volunteers to spend half the year in the underworld, during which time Dumuzi can go free.

The Ishtar myth presumably had a comparable ending, Belili being the Babylonian equivalent of Geshtinanna.