In the era of Satyuga, Diti’s son Daityas and Aditi’s sons, the Devas dominated the world. One day, they thought if there was any way through which they could become immortal and immune to every sort of disease, illness, laxity and fatigue. After cogitating, they finally concluded that the only way to achieve their hard-to-attain desire was by obtaining Amrit- the living giving elixir. But obtaining Amrit was not going to be an easy task. They only possible way to obtain Amrit was by churning the ‘Ksheer sagar’. By getting Mandrāchal mountain as the whisk and Vāsuki Nāga as the rope, the Daityas and Devas began churning the ocean of milk, which would give them the Amrit.
Both the factions relentlessly churned the ocean for over a thousand years. At last, something rose from the depths of the ocean, but to deva’s utter dismay, it was not Amrit, it was Halāhal - the poison. Halāhal could vanquish the entirety of earth and all the lives who dwelled there in a fraction of seconds. The Daityas and Devas watched in horror as Halāhal continued to rise from the ocean. Not being able to find any way to prevent the Halāhal, the Devas prayed upon Bhagwān Shiva. ‘Trāhimāma’, cried the Devas. Their prayers were answered and Bhagwān Shiva appeared in front of them. Even Bhagwān Vishnu manifested himself there.
‘O highest among the gods, since you are foremost among the gods, the first thing which would emerge from the ocean should be yours. Kindly accept the Halāhal.’, said Bhagwān Vishnu.
After seeing the obviously fear-stricken Devas and Daityas and hearing the words of Bhagwān Vishnu, Bhagwan Shiva decided to accept the Halāhal for himself. He drank the Halāhal and placed it in his throat.
Now that the threat of Halāhal was over, Daityas and Devas began churning the ocean once again. But another impediment obstructed their way, the Mandrāchal mountain toppled and fell reduced to the Pātala lok. At the moment, Bhagwān Vishnu at the behest of Devas and Daityas, manifested himself as a Kacchap- a turtle and sat deep inside the ocean, offering stability by bearing the weight of the mountain over his back.
Many years passed by and at last many beings and objects started manifesting from the ocean one-by-one. Dhanvantri, the god of Āyurveda rose from the ocean, holding a danda in his one hand and a Kamandal in the other. Soon after, 60 crore Apsarā of divine beauty and grace manifested. Then, Surā, the daughter of Varuna rose from the ocean and joined the faction of the Devas. Since the Daityas could not have Surā for themselves, they came to be known as Asura. This was followed by the appearing of Ucchaisharvā, the gloriest among the horses and a daimond called Kaustubh.
Finally came the moment for which the Devas and Daityas were waiting with baited breathes. From the waves of the ocean rose the Amrit, the life giving elixir, a drop of which could make anyone immortal and immune to any disease and fatigue. Wanting the Amrit for themselves, both the parties drew daggers against each other. A terrific battle ensued between the two, in which the Devas and Daityas fiercely fought each other.
Bhagwān Vishnu, assuming the form of Mohini, stole the Amrit and took it with himself. The battle culminated and the Devas prevailed. After vanquishing umpteen number of Daityas, Indra took the reigns of all the worlds in his hands.