Story of Ekadashi Vrat happened during the Satya Yuga and is
mentioned in the Puranas. Legend has it that Bhagavan Srihari Vishnu was
engaged in battle with Demon Mura during the Satya Yuga.
The battle went for several days and feeling tired Bhagavan
Vishnu decided to rest.
However, Demon Mura decided to attack Srihari Vishnu while
he was sleeping.
Suddenly a young girl appeared from the body of Bhagavan
Vishnu and she annihilated demon Mura.
She was the primordial mother and pleased with Her, Srihari
Vishnu called her Ekadashi as she appeared on the eleventh day of the
fortnight.