The origin story of Devshayani Ekadashi involves King Mandata, who inadvertently killed Sage Vashishtha's son during a hunting expedition. To cleanse his sin, the king observed this Ekadashi and was absolved of his guilt.
It is considered highly auspicious to observe this Ekadashi by fasting and praying to Lord Vishnu, seeking his blessings for prosperity, peace, and spiritual upliftment.