Indira Ekadashi takes place during the Krishna Paksha of Padmanabha (Ashvina) month. It falls during the sacred Pitru Paksha (the fortnight of ancestors). Observing this fast with pure devotion and offering the results to deceased ancestors has the legendary power to instantly release them from any hellish suffering.
In Satya Yuga, there was a glorious King named Indrasena who ruled the kingdom of Mahishmati. He was extremely wealthy, pious, and lived in complete spiritual harmony. One day, while the King was in his court, the divine Sage Narada Muni descended from the heavens to visit him.
Narada Muni shared a message from the King's deceased father. The sage explained that while traveling through Yamaloka (the realm of death), he saw the King's father suffering due to some minor spiritual discrepancies in his past life. The father had requested Narada to tell his son Indrasena to observe the upcoming Indira Ekadashi and transfer the merit to him so he could ascend to the spiritual world.
King Indrasena strictly observed the fast on the sacred day, along with his family. On the next day, they offered the spiritual merit of the fast to the deceased father. Miraculously, celestial flowers rained from the sky, and the father was instantly freed from Yamaloka, ascending to Vaikuntha on a radiant bird. Indrasena also lived in peace and eventually returned to Godhead, proving the immense redemptive power of Indira Ekadashi.