Legend of Onam festival.
Kashyapa had two wives, Diti and Aditi, who were the parents of demons and demigods (Asuras and Devas) respectively. As the common practice in those days, for a King invading another kingdom to acquire additional territory, Indra, the king of demigods went on war with the king of Asuras. Mahabali, the King of Asuras defeated Indra and proceed to occupy Indra's territory. Kashyapa, who had gone to the Himalayas to do penance, on his return, found Aditi weeping over the defeat of her son, Indra. By divine insight, Kashyapa recognised the cause of grief. Kashyapa tried to console Aditi who was wailing in grief, saying that nothing happens in the world without God's will and people should go on doing their duties. Kashyapa asked Aditi to pray to Lord Narayana and taught her Payovrata, ritual that has to be observed from the twelfth day of the bright half Karthika (Sukla-paksha Dwaadasi). Since Aditi carried out the Vrata with a pious heart, Lord Narayana appeared before her and informed her that he would himself take birth in her womb and help Indra. Later, on the twelfth day of the bright half of the month of Bhadrapada, Aditi gave birth to a son of uncommon effulgence. That child, "Vamana-murti", demonstrated His divine powers by doing marvelous deeds even when he was a child.
Balichakravarthi (Bali, The Emperor) or Mahabali, was the grandson of Prahlad, the son of Hiranya Kashyapu who was slayed by Vishnu in his Narasimha avatar. Hiranyksha the brother of Hiranya Kashyapu was slayed by Vishnu in his Varaha Avatar earlier. Prahalad being an Asura had great faith in Vishnu but his father, who was a devotee of Lord Brahma was very angry and hated all other Devas but Lord Brahma. One cannot miss the series of warfare between Vishnu and the Asuras - those born of the breath of God. Asuras did not acknowledge Vishnu as God. Bali Maharaj, sat in Prahlad's lap as a child and learnt love and devotion of Lord Vishnu from Prahlad. The Keralites perform the Mohiniattam, a dance dedicated to the female form of Vishnu, Mohini. There is also the dance Krishnanaattam.
Mahabali who was performing the sacrificial rite of Viswajith at the banks of Narmada River, (Central India) and declared that he would give anything that anyone sought from him during this Yagna. At this the gods were very annoyed. Bali was the ruler of all the three worlds having defeated the devas. The gods approached Vishnu and asked for his help to dethrone Mahabali. Vishnu, incarnated in the form of Vamana, a dwarf to defeat the Daityas.
