Today, we have a story behind a curse which was very crucial in the killing of Mahishashura by Goddess Durga, the celebration of Navaratri. Truely, if this curse would not be there, then we might not have the blessings of Goddess Durga with us.
Mahishasushara did the hard penance to please Brahma. Brahma blessed him with two boons:
1. He cannot be slayed by any human, god or demon.
2. He can transform his body to any living form.
One day Mahishasura took the form of a girl and entered into the ashram of Sage Katyayana when he was meditating. He went and drank the the Kheer (pudding which was meant to be offered to the gods). When sage katyayana realised this he asked the girl, “why did you had God’s food?” At that instant the girl turned into mahishasura and showed that he can transform into any form. Then Sage Katyayana gave him a curse that since you tricked me in the form of girl, you will die by a girl only. Mahishasura laughed at him and said, “When no human, god or demon can kill me, what harm can a girl do?”
Later all the Gods assimilated all their powers to give rise to Goddess Durga in the ashram of Sage Katyayana who went on to kill Mahishasura, That’s why the sixth form of Navadurga is called Katyayani (the daughter of Sage Katyayana). Read here the complete story how Goddess Durga killed Mahishasura.