The Durga Mahatman, Durga Puran or the Chandi as the book is known narrates the story of the Goddess. It tells how the Goddess killed numerous demons including the dreaded buffalo demon, Mahishasura.  Many many days ago in the city of Kola there was a king called Surath who was ousted from his land by his own ministers whom he trusted a lot. He fled into the jungles, lost his way and found himself in front of a beautiful hermitage.

He stepped inside. That was the ashram of the rishi Medha. The sage welcomed the king, and Surath started staying there. The atmosphere was serene. Birds used to sing, animals used to prance around and everyone was very happy.Surath was not at peace. He used to think about Kola all the time. One day there arrived a stranger in the ashram.His name was Samadhi. His wife and children had grabbed all his land and wealth and had driven him out of the house.

Samadhi started staying in Medha Rishi's ashram but his thoughts were still with his wife children. 
Both Surath and Samadhi then approached the rishi Medha oneday. hey wanted to know, how they could rid their lives of the worries they had. 
Medha started talking to them. He said 
Maya is the creator of attachment. Even though you are intelligent men you are behavng foolishly because of the Maya created by the great Goddess Mahamaya. Not only are the mortal beings victims of Mahamaya's Maya, even the Devas are not spared. She is the Eternal One. To save the world from the cluthches from the forces of th evil ones, she takes various avtaars. 
After the MahaPralaya, creation was destroyed. Everything was under water. On that water, Shree Vishnu was resting on the coils of the AnataShesh. The rest was a YogaNidra created by the YogaMaya. From the navel of Vishnu, out came a lotus flower, on which was seated Brahma. From the dirt of Vishnu's ears, suddenly two demons, Madhu and Kaitava took birth. Seeing Brahma in front of them, they rushed to kill him. Brahma then started praying to Yogamaya. Pleased with Brahma's prayers, Yogamaya released her spell from Vishnu who then woke up. Vishnu attacked the two asuras empty handed. A fierce battle started. Under the spell of Mayamaya's Maya, the asuras told Vishnu to ask for a boon which they would grant. Vishnu said then let your edath be from my hands. The Asuras looked around and said, So be it, but you will have to kill us in a place where there is no water. Vishnu then caught the asuras by the locks of their hair and using his Sudarshana Chakra, beheaded them. 
Once , the buffalo demon began praying to Brahma. Brahma gave him a boon, that he would die only in the hands of a woman. Believing that he had become invincible, Mahisha along with his asuras attacked the devas. A fierce battle took place between the Devas and the Asuras. The Devas lost and the Asuras then captured the heavens. The Devas fled to the Earth. There along with Brahma they started praying to Mahamaya. Thinking of their plight, the Devas became angry. There faces started glowing. The glow took the form of a bright light. That light took the shape of a many handed woman. The devas offered the Devi a weapon each. They gave her wonderful dresses and Himalaya offered her a Lion. Astride the lion, the devi began to roar. To see what had happened, Mahishasura came out of his palace. The big worriers in Mahisha's army,(Chikshur, Chamar, Mahahanu,Biralaksha, Vakshal) ¢Qr¥l, Q¡jl, jq¡qe¨, ¢hs¡m¡r, h¡úm, attacked the Goddess. The Goddess killed them all. Then Mahisha attacked the Goddess. Assuming the shape of a wild buffalo and using his hooves, tail and mouth, the asura started hurting the devas who were there to assist the Devi. The Devi then caught Mahisha in a noose. Mahisha then assumed the shape of a lion. The Devi chopped the Lion's head. Mahisha then assumed a man's form. On killing that, the asura assumed the form of a elephant. The Devi chopped off the elephant's trunk. Mahisha again assumed te form of a buffalo. The Devi picked up a bowl of nectar, and slowly sipping that she looked at Mahisha and said : Suddenly, the Devi jumped on Mahisha's back. With one foot she pressed down his throat and she pushed her (trident)n§m into Mahisha. Mahisha assuming his demon form emerged from the buffalo. Using her sword, the devi then chopped off Mahish's head. Mahisha died. 
The Devas began praying to the goddess. They said Maa, you have created this universe. You are the strength of all. Devatas, Rishis, Yakhas, Kinnaras all pray to you. Even Brahma, Vishnu and Mheshwar donot know you fully. For the Dharmik you are Lakshmi, for the adharmis you are Alakshmi. You are Buddhi, you are Lajja, you are shraddha. You were there lways and will be there forever. You are the adhar for all, You are Prakriti. You are Swaha. You are Swadha. You save the earth by killing the numerous asuras. After Mahishasura, two more demon brothers, Shumbha and Nishumbha started troubling the asuras. They forcibly snatched off the heaven from the Devas and pushed tem away. The devas then started praying to Mahamaya. At that moment, Parvati was going to have a bath in the river. She asked the Devas whom they were praying to. On listening to their tale of woe, from Parvati's body emerged a female form, Devi Kaushiki. Upon the emergence of Kaushiki, Parvati's body turned black and she then became known as Kalika. Kaushiki was spotted by Chanda and Munda, Shumbha Nishumba's two assistants. They reported to their masters, that they had seen a beautiful woman.Shumbha then sent a messanger to Kaushiki. The messanger, Sugriva, went to Kaushiki and said My masters Shumbha andNishumbha are the rulers of the heavens. They have sent me to you. They want you to marry either Sumbha or Nishumbha, the choice is yours. The Devi said I am foolish woman. I have made a very stupid promise that I will marry only that person who can defeat me in warfare. Tell your masters, whoever can defeat me in battle can win me. On hearing this, Shumbha sent Dhumralochana to capture the devi. Initially the asura tried to persuade the devi to accompany him, but when she refused, he rushed to capture her. The Devi uttered a manta and the asura was reduced to ashes. On hearing this, Shumbha sent Chanda and Munda to capture the Devi. On seeing Chanda nad Munda coming, the Devi wriggled her eyebrows. From the eyebrows emerged a ferocious looking Devi with a sword and a noose in her hands. She was wearing a tiger skin around her body. Her big eyes were red and from her tongue salive was flowing. She was Kali. Kali jumped among the asuras and started killing them. She killed Chanda and Munda and dragged their bodies to Kaushiki. She said