The Real Story:
It is believed that once the gods(devtas) were cursed by Rishi Durvasa. This made them lose their powers, thus weakening their body and mind. To regain their old strength and vigour, the devtas planned to churn the primal ocean to extract the 'elixir of immortality', the 'amrit' or 'the water of life'. They approached demons (daityas) and persuaded them to perform 'Samudra Manthan' (churning of the ocean) to bring out the nectar. One who would drink the nectar would become immortal and therefore, most powerful and indestructible. Thus, gods and demons agreed to share the nectar once it was brought up from the depths of the ocean.
The Huge Tug Of War:
Finally, the churning of the ocean began with the Mandar mountain being used as the churning stone and the giant serpent to become the coiled rope for turning. There was a dispute as to who would take which side - the head or the tail - of the serpent. Finally the churning began with the gods catching hold of serpent's tail and the demons, its head. Then started the huge tug of war.
As the churning progressed, the ocean began to yield its treasures. A deadly poison was produced and Lord Shiva came forth to swallow the poison to save the creation. The universe was gifted with a celestial horse, a divine cow, a valuable gem, a magic moon, a musical instrument, apsaras or beautiful dancing girls, Lakshmi (the goddess of fortune), Vishvakarma (the divine architect and constructor) and then came the divine medicine man, Dhanvantri, with the coveted pot of amrit.
The Last Spell:
Seeing Dhanvantari with the pot of nectar, the gods and demons became anxious. The demons who were physically stronger than the gods forcibly seized the pot. The demons and the Gods fought over the pot for twelve days and twelve nights (equivalent to twelve human years). Finally, Lord Vishnu, disguising himself as an enchantress, took the pot of nectar from the demons and passed to Jayant, Lord Indra's son, who assumed the form of a large bird, flew off with the jar. Some drops of the nectar fell on his way at four places: Allahabad, Haridwar, Trimbakeshwar and Ujjain. Each of these places became the holy pilgrimage sites for Kumbh Mela.
