LEGENDS OF DURGA
The principal source of legends revolving around the Goddess Durga is the 'Durga Saptashati' (seven hundred verses in praise of Durga), which forms a part of 'Markandeya Purana'.
The Supreme Mother Goddess or 'Mahamaya' is symbolic of the Primal Energy of the Almighty and epitome of the whole of Divinity that manifests itself into different forms depending on the need of the circumstances. As a creative energy and the giver of life, She has been revered as The Goddess Bhavani; as a slayer of evil and a principal force against negative forces, She is worshipped as Durga, and during the time of 'Pralaya' or the Final Dissolution, She takes the form of Kali.
As the Slayer of the demons Madhu and Kaitabh
The first reference of the Goddess in the mythological context can be found in the tale of how Lord Vishnu had destroyed the demons 'Madhu' and 'Kaitabh'.
It is believed that after the 'Pralaya' (the final dissolution), when Lord Vishnu was sound asleep, two demons- Madhu and Kaitabh, came into being from his earwax and proceeded to destroy Lord Brahma who was meditating on a lotus rooted in the navel of Lord Vishnu. Sensing the trouble, Brahma started to pray to the Great Goddess Mahamaya who is the ultimate and primal power of the universe, to break the great sleep of Lord Vishnu, so that he can save him. The Goddess granted Brahma's prayers and not only brought Lord Vishnu out of his sleep, but confused the minds of the two demons so that Vishnu could slay them easily.
The second reference of the Goddess is in the form of Durga, depicted with ten hands, three eyes; which denote the sun, moon and fire. The ten hands of Ma Durga holds various weapons and symbolizes that she will protect her disciples from all directions. She emerged in this form to slay the terrible buffalo demon Mahisashur, who wreaked havoc in the heavens and even managed to dethrone Indra, the king of the Gods.
The Goddess came into being from the collective energies (Shaktis) of all the Gods in a radiant, divine form. Her face was created by the grace of Lord Shiva. Her eyes were an aspect of Agni. Vayu's power created her ears. Her nose was created by Kubera's grace. Her teeth were from Brahma's power. Her lower lips were created by Surya's lusture. Her upper lips were from Kartikeya's (Skanda) grace. Her arms and shoulders possessed the power of Vishnu. Her fingers were created from the power of the Vasus. Her hips were created by Indra's lusture. Her thighs and knees were from Varuna's lusture. Her backside was of the Earth. The Gods then armed her with their weapons. Lord Shiva gave his trident, Lord Vishnu gave his discus or Sudarshan Chakra, Varuna gave a conch and noose, Agni gave a spear, Vayu gave a bow and arrows, Indra gave his Vajra or thunderbolt, Yama gave a sword and shield, Vishwakarma gave an axe and armour, Himavat gave a lion to mount and Jewels, and other Gods gave a lotus, ornaments and other magical offerings.
Each of the Goddess's weapon has a symbolic significance -
Chakra - The Sudarshan Chakra that spins in the little index finger of the Goddess symbolizes righteousness or 'dharma'. The Goddess uses this weapon to destroy evil and protect righteousness.
Conch - This is seen in her first upper left hand. The Conch stands for the cosmic sound of 'Om' vibration. The sound destroys all evil negative forces and when one prays to her, the vibrations fill one with peace and tranquillity.
Bow and Arrow - She holds them in her second left hand to destroy the difficulties arising in one's path in life. Her blessings are needed for success in all spheres of life. All hindrances get removed by this powerful weapon.
Sword - She holds it in her second right lower hand that depicts knowledge and keen intellect. She bestows one with the gift of knowledge to remove the veil of ignorance that binds a soul due to wrong deeds and karmic entanglements.
Spear - This weapon helps to destroy the negative and evil forces and grants auspiciousness.
Club - This is seen in her third right lower hand. This weapon destroys the power of the enemy, however powerful he may be. Durga's grace will help defeat one's enemies in life through the power of this weapon.
Trident - Trishul or trident seen in her fourth left hand symbolizes the three qualities - 'sattwa', 'rajas' and 'tamas' in a human. These qualities have to be balanced to lead a peaceful life. Her grace will give one the courage to fight the dark qualities arising in one due to the imbalance of the three qualities.
Thunderbolt - This weapon symbolizes firmness of spirit. Praying to Mother Durga will help shatter the problems encountered in life without losing confidence. She empowers her devotee with unshaken confidence and will.
Lotus - It stands for awakening of spiritual consciousness in a soul. Divine Mother will help her devotees to understand the transience of life and seek the ultimate truth.
Armed with their weapons and imbued with their qualities, Ma Durga fought the demon chieftains Chikshur, Chaamar, Udagra, Karaal, Vaalkal, Tamra, Andhak, Atiloma, Ugamya, Ugraveerya, Mahahanu, Vidaalasya, Mahasur, Durdhar and Durmukh first and slain them all. At last the shape-shifting demon Mahisashur appeared in various forms of man, elephant, buffalo, etc. To resume duel with the Goddess and was ultimately destroyed. Thus she is also known as Mahisamardini. The image of Durga, the Eternal Mother destroying the demon, Mahishasur is symbolic of the final confrontation of the spiritual urge of man with his baser passions.
Legend of the Pandavas
As per the Mahabharata, Pandavas after wandering in the forest for 12 years in anonymity, hung their weapons on a 'Shami' tree and entered the court of king Virat to spend the last one year in disguise. After the completion of that year on Vijaya Dashmi the day of Dussera they brought down the weapons from the Shami tree and declared their true identity. Since that day the exchange of Shami leaves on Dassera day has become symbols of goodwill and victory.
Legend of Lord Rama
Durga Puja has immense mythological significance. As per Ramayan, Rama did "chandi-puja and invoked the blessings of Durga to kill Ravana, the ten-headed king of Lanka who had abducted Seeta and had kept her in captivity. Devi Durga divulged the secret of vanquishing Ravana to Rama. After defeating Ravana Lord Rama, Sita and Lakshmana entered Ayodhya on the day of Diwali.
Apart from these legends, there are detailed discussions about Durga in Kalivilasatantra, Kalikapurana, Devibhagavata, Mahabhagavata, Vrhannandikeshvarapurana, Durgabhaktitarabgini, Durgotsavaviveka, Durgotsavatattva.