Shri Shantadurga 

There was a demon called Mahishasura. By securing a boon from Lord Brahma that if at all he were to be killed, only a woman should kill him, he became very powerful and started troubling the innocent by assuming the form of a buffalo(mahisha). Then with his vast army of demons he waged a war against Indra, the Lord of Swarga and dethroned him.  On account of his atrocities living became difficult in al the three worlds and so Lord Brahma accompanied by Lord Shiva and other devas approached Lord Vishnu to find out a solution. It was a huge assembly of all gods and as they were deliberating upon the problem and the probable solution, all of a sudden from their bodies emanated  divine splendour and brilliance which soon was transformed into a woman of unmatching beauty. She announced that she was the Mother of Universe and the very source of all energy. She also declared that the purpose of her appearing before them was to assure that she would destroy the wicked demon Mahishasura. All devas gleefully welcomed Jagadamba offering their salutations and prayers. They named her Durga and gifted her their favourite weapons. She mounted on her carrier, a lion and started the victory march. The fierce battle with Mahishasura took nine days and nine nights (Navaratri) and on the tenth day (Vijaya Dashami Day) she killed the demon Mahishasura and released the universe from the clutches of the wicked demon and his men.

 Shri Shanta Durga:

 As the legend goes  Shri Vishnu and Shri Mahesh were locked in a fierce battle. At the behest of Shri Brahma, Mother Goddess Durga intervened and pacified both of  them.  On account of Her, there was peace, “Shanti” and She became Shantikari Durga—Shanta Durga (and also Shanteri).

 In Devi Bhagwat Puran a mention has been made that Mother Goddess Durga divided herself into three parts, Shri Saraswati, Shri Lakshmi and Shri Parvati and became the consorts of the trimurtis, Shri Brahma, Shri Vishnu and Shri Mahesh. Therefore while worshipping them one may find common mantras and common names. “God is one and names are many,” this is what the Vedas have declared long time ago.