Long ago there was a wicked demon King- Mahishasura. He wanted to be powerful and rule the three worlds.
Therefore, he performed severe penance to please Lord Brahma.
When Lord Brahma was pleased and appeared before him, Mahishasura asked a boon- to be immortal- that is to never die. But Lord Brahma said “Mahisha- all that is born must die. That is the universal law. You cannot escape that”. Mahishasura thought for a while and said “if I must die, my Lord, it should be in the hands of a woman”.
Lord Brahma agreed and granted him the boon and returned to his abode.
Mahishasura thought- How can a woman kill a man? That is Impossible. I am now the most powerful person in the whole universe.
Mahishaura immediately ordered his army to attack the humans on the earth and the Gods/ Devas in the Devaloka.
Mahishasuar and his men became a menace- they started bullying and destroying the Devaloka and no one could touch him.
The King of Devas- Indra went to the Trimurtis- Brahma, Vishnu and Siva and explained the situation to them.
The three Gods created a powerful woman with several hands.
Lord Shiva offered his trisoola to Her.
Maha Vishnu his Sudarsana chakra
Lord Indra his Vajrayudha- or thunderbolt.
They named her Durga.
Durga- now, a powerful Goddess armed with inner strength, courage and wisdom with arms gifted by the powerful Devas set out on a lion to destroy Mahishasura.
Mahishasura’s heart skipped a beat when her heard the thunder of Goddess Durga’s arrival.
Still, he asked “A mere female trying to attack me?”
Durga responded “I not an ordinary female, Mahisha. I am here to fulfil your desire to be killed by a woman”
He immediately realised it was a danger sign for him and changed himself into a buffalo and charged the Goddess with all his might.
Durga with her inborn power and acquired weapons killed Mahishasura after a long battle.
The day Goddess Durga killed the wicked demon Mahishasura is celebrated as Vijayadasami . This day is also celebrated as a victory of Good over Evil.