Amrit Manthan Samudra Manthan समुद्र मंथन.
Inder Dev , the King of Svarga, while riding on the elephant Airavata, came across Sage Durvasa who offered him a special garland given to him by Shiva . Indra accepted the gift and placed it on the trunk of the elephant as a test to prove that he was not an egoistic deva. The elephant, knowing that Indra had no control over his own ego, threw the garland on the ground. This enraged the sage as the garland was a dwelling of Sri (fortune) and was to be treated as a prasada or religious offering. Durvasa cursed Indra and all devas to be bereft of all strength, energy, and fortune.
In battles following the incident, the Devas were defeated and the Asuras, led by Bali, gained control over the universe. The Devas sought Vishnu help, who advised them to treat the Asuras in a diplomatic manner. The Devas formed an alliance with the Asuras to jointly churn the ocean for the nectar of immortality and to share it among themselves. However, Vishnu told the Devas that he would arrange for them alone to obtain the nectar.
The churning of the Ocean of Milk was an elaborate process: Mount Mandara was used as the churning rod, and Vasuki, a nāgarāja who abides on Shiva’s neck, became the churning rope. The Asuras demanded to hold the head of the snake, while the Devas, taking advice from Vishnu, agreed to hold its tail. As a result, the Asuras were poisoned by fumes emitted by Vasuki. Despite this, the Devas and the Asuras pulled back and forth on the snake’s body alternately, causing the mountain to rotate, which in turn churned the ocean. When the mountain was placed on the ocean, it began to sink. Vishnu, in the form of the Kurma turtle, came to their rescue and supported the mountain on his shell.
The Samudra Manthana process released a number of things from the Ocean of Milk. One was the lethal poison known as Halahala, which in some versions of the story, escaped from the mouth of the serpent king as the demons and gods churned. This terrified the gods and demons because the poison was so powerful that it could destroy all of creation. Then the gods approached Shiva for protection. Shiva consumed the poison in an act to protect the universe, and his consort, Parvati, grabbed Shiva’s throat in an effort to prevent the most deadly poison from affecting the universes inside Shiva. As a result, his throat turned blue and was hence called Neelakantha (the blue-throated one; “neela” = “blue”, “kantha” = “throat” in Sanskrit).