The three worlds under Bali
King Bali, grandson of the great bhakta Prahlada and son of Virochana, ruled the three lokas with such daan and dharma that his fame outshone Indra's. No sadhu who arrived at his gate ever left unsatisfied; no promise once made was ever revoked; no oppression touched his praja. The devas, driven out of Swarga, went weeping to Bhagwan Vishnu — for the shastra allows a demon king who out-dharmas the devas to keep what he has won.
The Vamana avatar and the three steps
Vishnu took birth as the dwarf Vamana, son of Aditi and Kashyapa, and walked one day to the great yajna of Bali on the northern bank of the Narmada. He asked, in the small voice of a Brahmin boy, only for three paces of land. Bali laughed and consented against the warnings of his guru Shukracharya. The moment the sankalpa-jal touched Vamana's palm, he grew — vaster than mountains, vaster than sky. In two paces he measured the earth and the heavens; for the third pace, no ground was left.
Bali's surrender
Bali, without flinching, bowed his head and said, 'Prabhu, place the third foot here.' Vamana pressed his lotus foot upon the king's head and sent him down to Sutala, a beautiful realm below the earth. But pleased beyond measure by the daitya's surrender, he granted Bali sovereignty of Sutala forever, promised to guard the door of Bali's palace personally, and swore to visit him in Chaturmas each year. To honour him, Vishnu chose this Bhadrapada Shukla Ekadashi — in the middle of his own yog-nidra — as the day he would turn onto his side, so that his own face during rest would remain forever towards Bali.
The vrat of parivartana
Devotees observe this Ekadashi to honour that great turning: fast the day, keep jagran with Vishnu Sahasranama, and at Dwadashi parana offer saffron-yellow rice with curd, and dakshina to a Brahmin. The shastra says that on this night, so pleased is Bhagwan Vishnu by the memory of Bali, that whoever chants Vamana-naam even once with faith receives the same grace of eternal darshan that was given to the daitya king.
"Grants Vishnu's personal protection and darshan at the moment of death. Especially auspicious for those beginning a new phase of life — a marriage, a business, a move — under his turned gaze."