Long ago, Rambha, the king of Asuras, fell in love with a princess. Her name was Shyamala and she was cursed to be a buffalo. From their union a boy was born. The boy Mahishasura could take the form of a buffalo or an Asura as he wished.
Mahishasura became a formidable warrior when he grew up. In order to become even more powerful, he performed a severe penance to lord Brahma. When lord Brahma was happy with his sincerity and sacrifice, he gave him a boon that no man, Deva or animal could ever kill him.
Empowered by the boon, Mahishasura amassed a huge army of Asuras and started tormenting the creatures on the earth. Soon the earth was under his grip.
Not content with his achievement, Mahishasura wished to overpower the gods in the heaven. After a severe battle, he defeated the Devas and took over the heaven.
The Devas, accompanied by their king Indra, came to Brahma, Vishnu and Shiva for help. To fight Mahishasura, the trinity decided to combine their powers. Three dazzling pillars of light emerged from them and joined together. Other Devas also contributed their power to the bundle of light.
Then the glowing bundle of light took the form of goddess Durga. She possessed exquisite beauty and multiple hands. The gods showered her with many precious gems and jewelry.
Then they gave her their special weapons. Brahma gave her the Kamandala filled with holy water. Vishnu gave his Sudarshana chakra. Shiva gave his Trishula. Indra gave his lightening thunderbolt called Vajra. Varuna gave her a conch that made sounds capable of rising terror in the hearts of the enemies. Agni, the lord of fire, gave her a deadly weapon called Sathagni. Vayu gave her a bow and a quiver that never ran out of arrows. Himavan, the king of mountains gave her a lion to ride.
Then all the Devas bowed to her and addressed her as mother. They pleaded her to save them from the mighty Mahishasura. After giving assurance to them, Durga rode on to her lion which roared and walked toward the heaven.
When Mahishasura heard about the approaching of Durga, he sent many of his warriors to destroy her. But she slew them one after the other.
Finally, Mahishasura came to battle with her.
He took the forms of many vicious animals and charged on her. But he was unsuccessful in harming her. At last he came to his original buffalo form and ferociously attacked her. Goddess Durga finally took the Sudarshana chakra and beheaded Mahishasura, bringing an end to the buffalo-daemon.