Once upon a time, there lived a king named Mahabali. He was the son of Virochana and Devamba and was a generous and a benevolent king. He treated his people with equality and respect. He also gained his immortality by drinking the amrita (stolen by asuras from Gods) thus gaining immortal and power than the gods. After many wars, the invincible Bali had won the heaven and earth. The Gods approach Vishnu to save them. Vishnu refused to join the war or kill his own devotee Mahabali. He used a tactical approach instead and incarnated as the dwarf Brahmin avatar, Vamana. While Mahabali was performing Ashvamedha Vedic sacrifices to celebrate his victories and giving away gifts to everyone, Vamana approached him and asked for "three steps of land". Mahabali granted him the gift. Vamana then metamorphosed into Vishnu's giant Trivikrama form, taking all of heaven in one step and earth in second. Mahabali realized that the Vamana was none other than Vishnu and offered his own head for the third step. Some Hindu texts state that Mahabali became the king of Sutala (a world more beautiful than Swarga, where Vishnu himself attended to Mahabali), some state he entered heaven with the touch of Vishnu, while another version states he became a chiranjivi (immortal).
Vishnu granted Bali a boon whereby he could return to earth every year. The harvest festivals of Onam are celebrated to mark his yearly homecoming. Literature and inscriptions in temples suggest that these festivals, featuring colorful decorations, lighted lamps, gift giving, feasts and community events, have been popular in India for more than a millennium.
Onam a festival of auspiciousness and happiness is celebrated to await the return of Maveli or Mahabali. In this festival, People celebrate with an enormous Sadya with Payasam as a sweet alternative. People make the atham or rangoli in front of houses and enjoy with friends family and relatives.
Wishing everyone a Happy Onam and let prosperity and auspiciousness come to you from every side.
Thank you. Stay Safe..