Devayani standing besides Yayati, questions Sharmishtha
Sharmistha was the daughter of Vrisaparva, the Daitya king, for whom Shukracharya was an adviser. One day Sharmishtha, daughter of the Danava king Vrishparva and Devayani, daughter of the Daitya sage Shukracharya, go with Sharmishtha's retinue to bathe in a forest pool not far from their home. After bathing, Sharmishtha confuses Devayani's sari with hers and puts it on instead. Devayani returns, scolds Sharmishtha for her mistake and belittles her with the jibe that she is the daughter of Shukracharya (Shukracharya being a sage and high priest and indeed the guru of all the Asuras - no mere employee) as Vrishparva's and their Kingdom lives on his blessings. This slur on herself and her father Vrishparva infuriates Sharmishtha with the help of her servants throws the naked Devayani into a well and leaves the forest with her retinue. Later Yayati, son of Nahusha, comes to the well for water and helps Devayani to climb out of it. She tells him that as he held her right hand, he should be her husband. 
However, Devayani, still angered by Sharmistha's belittling her at the forest, plans her revenge on Sharmistha. She tells her father that she wouldn't go back to the capital until Sharmistha serves as a handmaiden for the rest of her life. Shukracharya also leaves the capital to stay with his dearest daughter. Seeing the plight of her father King Vrisparva, Sharmistha sacrifices her royal status and agrees to take up the role of a handmaiden to Devayani to protect the kingdom. Devayani comes back to capital along with her father and enjoys the servitude of Sharmistha.
Relationship with Yayati
Some days later Devayani goes to a picnic in the forest along with her Sharmistha and other servants. There Yayati comes for hunting and they meet again. This time she brings him to her father and tells him that they would like to marry. Shukracharya gives his consent and tells Yayati that he should take care of Sharmista too as she was a princess but shouldn't have nuptial relation with her. Yayati marries Devayani and looks after her well. 
After a while Yayati meets Sharmistha and is captivated by her beauty and intelligence. As fate would have it Sharmistha also fell in love with the King. She way laid him one day in his palace and declared her love for him. Yayati had been very much struck by her beauty all along, and was sorely tempted to return her affection. However, the promise made to Shukra and the fatal consequences that were sure to follow from his transgressions made him hold back. In the end, his passion proved stronger than his virtue and he took Sharmistha as his second wife who gives birth to three sons Druhyu, Anu and Puru.
Eventually Devayani comes to know about her husband's relation with Sharmistha and complains to her father. Shukracharya curses Yayati with old age for giving pain to his daughter. But later he tells him that if one of his sons could take his old age and give him his youth back, he could escape from the curse for some time. Yayati asks his sons for their youth but everyone rejects except Sharmistha's son Puru. Yayati makes him his descendant, who gives rise to Kuru vamsha later. Later Sharmistha is blessed for her sacrifices and is converted to a constellation after her death. The constellation Cassiopeia is the Western name for Sharmistha
- Dowson, John (1888). A Classical Dictionary of Hindu Mythology and Religion, Geography, History, and Literature. Trubner & Co., London.
- Mani, Vettam (1964). Puranic Encyclopaedia. Motilal Banarsidas, Delhi. ISBN 0-842-60822-2.