Onam-Legend of demon king "mahabali"

The legend says that Mahabali,an Asura (demon), was the king of Kerala.
He was a noble and virtuous king. Although he was an asur, he was known far and wide for his generosity and good sense. It is said that if a person asked Mahabali for something, he never returned disappointed. Mahabali defeated Indra and conquered heavens. However Mahabali was a worshipper of Lord Vishnu. Devaas (the Gods) sought the help of Vishnu to curb Mahabali's power.

Vishnu, took the form of a Vamana (dwarf) Brahmin (this was his sixth incarnation), approached Mahabali after his morning prayers when generous Mahabali would grant boon to Brahmins. Vamama asked for land for his prayers. Mahabali told him that he can have as much land he wished but Vamana said that he justed wanted land which could cover with his three steps which Bali accepted. As soon as Bali poured the sacrificial water into the hands of Vamama, he began to expand. With his first step, he covered the sky, blotting out the stars (the whole of heavens).

With the second step he covered the whole of earth and then asked where he should keep his third step. Mahabali offered his head as the last step. Vamana put his foot on Mahabali's head and pushed him down into the Patallok (the netherworld).

Moved by the nobility of this demon king, Vishnu proclaimed that even after losing every worldly possession, Mahabali would earn eternal wisdom and the love and affection of Vishnu. Mahabali asked for and was given one reprieve, that he be allowed to return once a year to visit his beloved subjects. Onam is the occasion when the righteous king makes his temporary return from exile. On the eve of Thiruvonam, the 2nd and the most important day of Onam, Bali comes to meet his people. In memory of the happy days of Mahabali's rule, a grateful Kerala celebrates his annual home-coming with all the pomp and grandeur it can command. This interesting legend is depicted in a very artistic manner at the Suchndram temple in Kerala.