Mahishasur", a Giant, son of "Rambha" became very powerful by the blessing of supreme God Brahma. All the demi-gods were attacked by Mahishasur and insulted by the Giant. Their king "Devraj Indra" was defeated and dethroned by him. At this situation, the king "Devraj Indra" with some of his fellow beings approaches Lord Brahma and Shiva to save them from the atrocities of the demon Mahishasur. They all decide to approach Lord Vishnu and plain him of the Mahishasur. Thus, headed by Lord Brahma and Lord Shiva all the demi-gods proceed to Lord Vishnu and brief him about the demon king and implored him enabling a plan to finish the wicked . Lord Vishnu, after hearing from them, told them that Mahishasurâ€™s death is very imminent in the hands of a young women. You all bestow, all your mighty powers there and go to your places and be happy." Thus hearing from the supreme personality of the Godhead, having been satisfied with the answer of the Lord all the demi-gods presented their specific powers to form the divine creation. As this happened, all the powers got together and formed as a bright and powerful mightiest force out of which a most beautiful and powerful femme fatale "Mahashakti" emerged. Then all the demi-gods became very happy and presented their powerful weapons to the Goddess. Then Brahma addressed the goddess- " Oh the mighty one! May your name be "Thrikala", and you shall always be protecting this world. Depending on the quality you will be invocated by many names . You expand in to the three different forms, as you see three colours in you". And thus Goddess expands into three different forms, which are of white, red and black. Out of Brahmaâ€™s potency" Mahasaraswathi", and out of Vishnuâ€™s potency "Mahalakshmi", and out of lord Shivaâ€™s potency "Mahakali" has been emerged".
In the cave, goddess is present in all these three forms and these three collectively known as "Vaishnavi". But there is no any other difference in these three forms. Though in appearance there is a difference, but the goddess is one in spirit. Only by nature of function the name differs. The three things like desire, intelligence and execution without which no task gets completed. In addition to this, there is yet another psychological reasons in this world if one has to lead a happy life, he has to be in possession of intelligence, wealth and good health. For attaining all these three, the process of worshipping the goddess is given.
The goddess (Adishakti) promised the demi-gods that as when the baddies rise and disturb them (demi-gods) she would incarnate and vanquish the demons. Thus to keep up her words the goddess killed the demons like- Mahishasur, Chand-Mund, Shumb-Nishumb and Rakthabeej and et'al. Hence, over the millions of years, on the Shatashrunga mountains, worship of Lord Vishnu being kept in by the Goddess â€˜Vaishnoâ€™ through meditation. As the goddess is a devotee of Lord Vishnu, power of Lord Vishnu and the purpose for executing Lord Vishnuâ€™s work has popularly been known as "Vaishnavdevi" or Vaishnoâ€™ throughout the universe. As was enumerated earlier- "Saraswati"," Mahakali" and "Mahalakshmi" together are called "Vaishnavdevi".