Mahabali

The three strides are older than Bali. In the Rigveda, Vishnu is the god who paces out the worlds in three steps, and the third step is set somewhere no one can follow; there is no dwarf, no asura king and no deception in those hymns. The story of a king who gives away the ground under his own feet is attached to that image later, in the Brahmanas and then fully in the Puranas, and Vamana, the dwarf, becomes the fifth avatar of Vishnu.

The Puranic version turns on a legal formality. Bali is holding a sacrifice at which he has undertaken to refuse no request. Vamana asks only for three paces of ground. Shukra, the guru of the asuras, sees exactly what is happening and tells Bali not to grant it. Bali answers that a king who has promised cannot take the promise back because the beneficiary turns out to be dangerous, which is the whole moral position the story exists to state. Shukra then tries to block the ritual water that would seal the gift by entering the spout of the vessel, and is pierced by a blade of darbha grass, losing an eye.

Bali pours the water. Vamana grows, covers earth with one stride and sky with the second, and asks where the third is to go. Bali offers his head. He is pressed down into the netherworld Patala, and in most tellings is granted rule there and the promise of a future office as Indra. The defeat is a promotion, delivered as a punishment, for a virtue nobody disputes.

Onam runs for ten days in the Malayalam month of Chingam, from the asterism Atham to Thiruvonam, and it is kept across Kerala by Hindus, Christians and Muslims alike, which is unusual for a festival with a Puranic story behind it. The reason is that Onam is also the harvest, and the observance is domestic before it is temple based.

The house is prepared for a guest. A pookkalam, a circular carpet of flower petals, is laid in the courtyard on the first day and enlarged each day until Thiruvonam. Small conical clay figures called Thrikkakara Appan are set up and worshipped in the home, named for the temple at Thrikkakara near Kochi that tradition identifies as Bali's seat. The Onasadya, a vegetarian feast of many dishes served on a plantain leaf in a fixed order, is eaten on the last day. Elsewhere there are the boat races of the backwaters, the Athachamayam procession at Tripunithura, tiger dances, swings hung for children, and new clothes given within families.

The framing matters as much as the customs. Onam is not kept as the anniversary of a demon's defeat but as the day a loved king is allowed home to see whether his people are still well and still honest, which is why the greeting and the songs speak of a time when all were equal and there was no deceit. Some modern readings in Kerala press that further and treat Bali as a native ruler displaced by an incoming order, a reading the festival's own affection for him makes easy to argue and hard to settle.