According to the Hindu mythology, Mahishasura was the king of demons who constantly wreaked havoc on the three worlds. The name ‘Mahishasura’, which literally means ‘a demon with a buffalo’s face’, is a combination of two words ‘mahish’ (buffalo) and ‘asura’ (demon). According to legends he was killed by Goddess Durga
following a fearsome battle 'that lasted nine days. Hence the goddess is referred by the name Mahishasuramardini
; the killer of demon Mahishasura. This victory of the good over the evil is celebrated all over India as Navratri
As the story goes, Mahishasura undertook a severe penance to obtain a boon from Lord Brahma. Pleased by his penance Brahma granted him a boom, according to which he would be invincible and could be killed only by the hands of a woman. Not afraid of any woman, Mahishasura went about causing destruction and defeating numerous gods. He even defeated Lord Indra, the king of demigods, and captured the throne of heaven. Seeking help Lord Indra approached the trinity in Hinduism; Lord Brahma, Lord Vishnu and Lord Shiva. Together these three gods created Goddess Durga, the personification of Shakti, to destroy the demon. Each of the gods gifted her with their celestial weapons to help in the fight.
Goddess Durga challenged the demon and the resulting battle continued for nine days. Finally on the tenth day she attained ‘Vijay’ (victory) by slaying the demon.