Onam is celebrated in Kerala in honour of Mahabali, the great demon king, who was known to be compassionate, kind-hearted, and generous. Every Malayalee has at some point in life heard the story of Mahabali.

A great devotee of Lord Vishu, he was loved tremendously by his subjects. He ruled his kingdom with fairness and justice. In Mahabali's kingdom, everyone was treated equally. There was peace, love, and people prospered under his rule.

The Mighty Mahabali was extremely popular among his subjects for his fairness, justice, and charitable nature.

Legend has it that the Gods grew jealous of Mahabali's popularity, and they requested Lord Vishnu to control him.

So, Lord Vishnu decided to test Mahabali's faith. Transforming into his Vamana or dwarf avatar, Lord Vishnu approached King Mahabali as a small Brahmin boy and asked for alms.

Mahabali welcomed the boy and washed his feet. He then told the poor boy that he would grant him anything in the form of alms. Vamana asked for three steps of land. 

An amused Mahabali was about to agree, when his advisor Shukra recognised Vamana's true identity and tried to stop Mahabali, who was about to seal the deal by pouring holy water from a kamandalu or pot. Shukra shrank to a tiny size and lodged himself in the vessel's spout. But Mahabali used a sacred grass to remove the obstruction, accidentally blinding his advisor in one eye.

The benevolent king agreed to the boy's request, and the minute he said yes, Vamana grew into his divine size. He was so enormous that he could touch the sky.

In one gigantic step, he covered the whole of heaven. His next step covered the whole of Earth, and there was no place for a third step, so Mahabali, who was fully prepared to honour his word, offered that Lord Vishnu place his foot on his head.

Mahabali knew his time was up and bent down at Vamana's feet.

However, before Mahabali was banished to the underworld, he was rewarded for his devotion and offered wish. The mighty asura king wished that he could visit his people once every year.

Every Onam, the Great Mahabali returns to visit his beloved people all the way from the underworld, and he is welcomed with great devotion.

Homes are decorated with pookalam or flower rangolis, traditional feasts or sadhyas are arranged, and Malayalees welcome Mahabali with great joy and aplomb during the ten-day Onam festival.