Mythology of Durga Puja
According to Hindu mythology a demon named Mahishasura, earned the favor of Lord Shiva after a long and hard penance. Lord Shiva, impressed with his devotion, blessed him that no man or deity would be able to kill him and that only a woman can kill him. Mahishasur was very pleased with this boon as he thought that a woman can never defeat him. Arrogant Mahishasura started his reign of terror over the Universe and people were killed mercilessly. He even attacked the abode of the gods and conquered the heavens and became their leader.

The Defeat Of Gods
After their defeat and humiliation at the hands of Mahishasur, the gods took refuge under Lord Brahma, who took them to Lord Shiva and Lord Vishnu. The only solution left was the creation of a woman who possess the ultimate power to fight and defeat Mahishasur. Pure energy blazed forth from Brahma, Vishnu and Shiva - the trinity forming the pure energy of Godhood, all concentrating at one point that took the form of Goddess Durga.

Culmination Of Energies
Her face reflected the light of Shiva, her ten arms were from Lord Vishnu, her feet were from Lord Brahma, the tresses were formed from the light of Yama, the god of death and the two breasts were formed from the light of Somanath, the Moon God, the waist from the light of Indra, the king of gods, the legs and thighs from the light of Varun, the god of oceans and hips from the light of Bhoodev (Earth), the toes from the light of Surya (Sun God), fingers of the hand from the light of the Vasus, the children of Goddess river Ganga and nose from the light of Kuber, the keeper of wealth for the Gods. The teeth were formed from the light of Prajapati, the lord of creatures, the Triad of her eyes was born from the light of Agni, the Fire God, the eyebrows from the two Sandhyas,ie, sunrise and sunset, the ears from the light of Vayu, the god of Wind. Thus from the energy of these gods, as well as from many other gods, was formed the goddess Durga.
Power Of Weapons
The gods then gifted the goddess with their weapons and other divine objects to help her in her battle with the demon, Mahishasura. Lord Shiva gave her a trident while Lord Vishnu gave her a disc. Varuna, gave her a conch and noose, and Agni gave her a spear. From Vayu, she received arrows. Indra, gave her a thunderbolt, and the gift of his white-skinned elephant Airavata was a bell. From Yama, she received a sword and shield and from Vishwakarma (god of Architecture), an axe and armor. The god of mountains, Himavat gifted her with jewels and a lion to ride on. Durga was also given many other precious and magical gifts, new clothing, and a garland of immortal lotuses for her head and breasts.

                The beautiful Durga, bedecked in jewels and golden armor and equipped with the fearsome weaponry of the gods, was ready to engage in battle with the fierce and cruel Mahishasura. Mahishasura and his demon allies found their attention drawn from heaven to Earth, as Durga's power moved its way towards heaven. Though confident of their power and control in heaven, the demons could not help being awestruck.

The Battlefield
As Mahishasura's armies were struck down effortlessly by Durga, it became obvious to him that he was not as secure in heaven as he had thought. No demon could fight her and win. Her breath would replenish her armies - bringing back to life all of her soldiers who fell. The demons were in chaos and were easily defeated and captured. Mahishasura was shocked and enraged by the disastrous events on the battlefield. He took on the form of a demonic buffalo, and charged at the divine soldiers of Durga, goring and killing many and lashing out with his whip-like tail. Durga's lion pounced on the demon-buffalo and engaged him in a battle. While he was thus engaged, Durga threw her noose around his neck.
             Mahishasura then assumed the form of a lion and when Durga beheaded the lion, Mahishasura escaped in the form of a man who was immediately face to face with a volley of arrows from Durga. The demon escaped yet again and then having assumed the form of a huge elephant, battered Durga's lion with a tusk. With her sword Durga hacked the tusk into pieces.
The Victory
The demon reverted once more to the form of the wild buffalo. He hid himself in the mountains from where he hurled boulders at Durga with his horns. Durga drank the divine nectar, the gift of Kuber. She then pounced on Mahishasura, pushing him to the ground with her left leg. She grasped his head in one hand, pierced him with her sharp trident held in another, and with yet another of her ten hands she wielded her bright sword, beheading him. At last he fell dead, and the scattered surviving remnants of his once invincible army fled in terror.