Mahabali is also known as Bali.
Bali was a Daitya ( an Evil King ) and the grandson of Prahlada.
After numerous wars, the unbeatable Bali had won “Heaven” and “Earth”.
The “Gods of Heaven” approached Lord Vishnu to save them from Bali.
Lord Vishnu refused to help as Bali was his devotee. But the ” Gods of Heaven” pleaded as they couldn’t take charge of activities in heaven.
So Lord Vishnu decided to take an incarnation of a dwarf Brahmin – Vamana.
When Mahabali was performing the “Ashvamedha”,the Vedic sacrifices, Lord Vishnu entered the scene as the Vamana.
When Mahabali asked Vamana in great pride, – “What do you want ?”
Vamana said he needed just-
“Three Steps of Land”.
Mahabali in his pride laughed and granted him the gift. Vamana then transformed into Lord Vishnu’s giant form called the “Trivikrama”.
Lord Vishnu started taking his ” Three Steps”.
The First Step he took was the “Heavens” from Bali ,
The Second Step he took was the “Earth”.
Vishnu then asks Bali where he should put the ” Third Step” as he didn’t have any place now.
To which Mahabali realized that he was the supreme, Lord Vishnu, and hence offered his own head for the third step.
Some texts say that when Lord Vishnu touched Bali with his feet he became Chiranjeevi or immortal.
It is said that Bali stayed in Heaven and was granted long life.
Lord Vishnu had even granted Bali a boon whereby he could return to earth every year.
It is believed that, in Kerala, the harvest festivals of Balipratipada and Onam are celebrated to mark his yearly homecoming.