As per Garuda Puran (I 240.26-28, Ramayana -III.35.27.34 and Mahabharata I-25.ff..) once upon a time sage Durvasa (spiritually enlightened sage) visited the capital of Swarga (heaven). The sage in pleasant mood intended to see Lord Indra and on meeting him affectionately offered garland of 'never wilting flowers'. Lord Indra took them in a casual way and passed the garland to Airawat (divine elephant) who in turn crushed the garland under his feet. Angered at Lord Indra's arrogance, sage Durvasa pronounced a curse on him, devoiding him of all the riches, virtues and power. Knowing this, demon King Bali attacked Lord Indra and snatched away all the riches and virtuous possessions. The gods were weakened and Lord Vishnu (the preserver of the Universe) advised Lord Indra that to regain his lost powers and splendour he needed ambrosia or Amrita (divine nectar). To extract this from the depths of the ocean, the demons were motivated to churn the ocean along with the Gods. Mighty mountain Mandarachal was used as churn staff, formidable serpent king Vasuki became the string to move the churn, Lord Vishnu in the guise of koorm (tortoise) gave support from the bottom and Lord Brahma (the creator of Universe) guided the churning from top.
With the churning, fourteen Ratnas (virtuous jewels) emerged from the ocean. These were Poison, Flying Horse, Magic Moon, Sky chariot, Vibrant Lyre, Rambha (the siren), Lakshmi (the paragaon of beauty and the provider of all riches), Vishwakarma (the divine architect), Dhanvantari (the divine healer), Gajaraj/Airawat (the divine elephant), Kaustubh Mani , the divine conch shell, Varuni (the enchantress) and the coveted kumbh (pitcher) of Amrit (divine nectar).
With the emergence of amrit, there was scramble amongst the gods and demons for the possession of the divine elixir. Lord Vishnu handed over the kumbh(pitcher) of amrit to divine Garuda (the winged mount of Lord Vishnu). Garuda, who was to take the pitcher of nectar safely to heaven(Swarga ), was stopped on way at four places by the demons. These places are the present day Allahabad, Hardwar, Ujjain and Nashik, where Garuda had to put the pitcher down. Some of the nectar spilled at these places, sanctifying them forever. (As per Skand Puran, the story of taking away the pitcher by Jayanta, son of Lord Indra and the episode of spilling of nectar is mentioned, while other Purans - Vishnu, Brahamandu, Padma, Bhagwat, Agni, Mahabharat and Ramayana narrate the story of Garuda the winged mount of Lord Vishnu.

All along the flight, Garuda was guided by Lord Brihasapati (Jupiter),then transiting in the rashi (zodiac) Acquarius, Taurus and Leo. Sun and Saturn alongwith the Moon were on the vanguard in protecting the Amrit Kumbh (pitcher of divine nectar). The flight of Garuda lasted 12 days (12 human years). Therefore Kumbh is celebrated around every twelve ye.