Mahabali

He was a legendary human king who ruled all of earth and was so rich, noble and generous that even the gods were jealous of him. They plotted against him and sent Vamana, a little brahmin boy, to Mahabali. Vamana asked him to grant him a boon which the generous king promptly agreed. Whereupon the brahmin boy asked for land which could be covered with his three steps. When the king agreed the Vamana suddenly took on a gigantic form and covered the earth with one foot, the skies with the second and asked the king where he should he place his third step. Though Mahabali realized that this was ploy of the gods but being a noble and generous king he offered his head to the Vamana. When Vamana stepped on his head Mahabali was pushed into the netherworld. But he promised his people that he would visit them once a year and Onam, a major festival of Kerala (Southern India), is the day he comes to see his people.

The keralites welcome his annual visit, on the day when the moon is on Shravana star in Capricorn and the Sun is in Leo. ie., in the luni-solar month of Simha (Lion).