In battles that followed this incident, Devas were defeated and Asuras (demons) led by king Bali, gained control of the universe. Devas sought help from Lord Vishnu who advised them to treat asuras in a diplomatic manner. Devas formed an alliance with asuras to jointly churn the ocean for the nectar of immortality and to share it among them. However, Lord Vishu told Devas that he would arrange that they alone obtain the nectar.
Churning the Milky Ocean
The churning of the Ocean of Milk was an elaborate process. Mount Mandaranchal was used as the dasher (churning tool), and Vasuki, the king of serpents, became the churning rope. The gods held the tail of the snake, while the demons (Asuras) held its head, and they pulled on it alternately causing the mountain to rotate, which in turn churned the ocean. However, once the mountain was placed on the ocean, it began to sink. Vishnu in his second incarnation, in the form of a turtle Kurma, came to their rescue and supported the mountain on his back.
As per (Hari Bhakti Vilasa 5/257 from Skanda Purana , 258/259 From Srimad Bhagvatam 11. 27. 12-14) a Shaligram Shila with Golden flow on a Shaligram Shila will represent the Nector that came out after the Samundra Manthan. These Shilas are very few on this Universe as where ever the drop of Nector fell, the Shaligram Shila has absorbed that nector and same has become golden flow and emerged out from the Shila. This Shila is Samundra Manthan Shila. There will be several ‘Akrutis’ of various Devetas and Demaons and the 14 Ratnas that emerged out during this churing of ocean that can be seen on the Shaligram Shila. The Shila blesses the devotee with spiritual enlightenment and rejunivation of positive energies and discarding of negative energies. This enlightens the consciousness like the wave of Ocean. It gives tremendous concentration and stability in thoughts like Mandara mountain. Vasuki represents the desires and we need to control our desires. The poison represents the difficulties, sufferings and pain in life and worshipper comes out of these difficulties by Karma Yog, Gyan Yog, Dhyan yog and Bhakti yog. Lord Shiva symbolises the will to take everybody’s responsibility on one’s shoulders, the awakening of “Super Conciousness”. Dhanvantri symbolises the good health and longitivity. The Nector symbolises the achieving of ultimate goal, the Salvation and Laxmi represents the universal enrichment and wealth to do good and selfless service to others.