Narakasura or Naraka is the asura son of the earth goddess Bhudevi (Bhumi) and Lord Vishnu in his Varaha (boar) avatar (incarnation) in Hindu mythology. Other sources claimed that he is the son of the asura, Hiranyaksha.
Narakasura is said to have established the kingdom of Pragjyotisha in Assam after overthrowing the last of the Danava king Ghatakasura. It was foretold that he would be destroyed by a later incarnation of Vishnu. His mother, the earth, sought the boon from Vishnu that her son should have a long life, and that he should be all powerful. Vishnu readily granted these boons.
Narakasura became evil, in association with another Asura named Banasura. Drunk with power, as he knew himself to be unrivaled in prowess, he brought all the kingdoms on earth under his control. Next, he turned his eyes towards Swargaloka. Even the mighty Indra could not withstand the assault of this son of Vishnu and had to flee the heavens. Narakasura had become the overlord of both the heavens and earth. His reign of oppression was in full swing. Addicted to power, he abducted 16,100 women and imprisoned them in his palace. He stole the earrings of Aditi, the heavenly mother goddess, and usurped some of her territory.
All the Devas, led by Indra went to Vishnu, to ask him to deliver them from Narakasura. Vishnu promised them that he will attend to this matter, when he will be incarnated as Krishna.
As promised to mother earth, Narakasura was allowed to enjoy a long reign. At last Vishnu was born as Krishna. Aditi, who was a relative of Krishna's wife Satyabhama (believed to be an Avatar of Bhudevi - Narakasura' mother), approached Satyabhama for help. When Satyabhama heard of the Narakasuara's ill treatment of women and his behavior with Aditi, she was enraged. Satyabhama approached Lord Krishna for permission to wage a war against Narakasura. As promised to the Devas and Aditi, Krishna attacked the great fortress of Narakasura, riding his mount Garuda with wife Satyabhama. The battle was furiously fought. Narakasura possessed 11 Akshauhini (a division of the army) that he unleashed on Krishna. However, the Lord slew them all with little effort. Krishna also killed Mura, Narakasura's general. In desperation, Narakasura launched his great weapon, sataghini (a thunderbolt) on Krishna. However, it made no impact whatsoever on Krishna. At last, when Narakasura tried to kill the Lord with a trident, Krishna beheaded him with his Sudarshana Chakra (discus). Before dying, the Asura requested a boon that his death anniversary should be celebrated by all people on earth. This day is celebrated as 'Naraka Chaturdashi' - the first day of Diwali.
In another version, Narakasura had gained a boon from Brahma that he would die only in the hands of his mother. On the day of the war, Satyabhama with Krishna fought Narakasura bravely, but she was no match to his trained skills. After a few days when Narakasura got a chance, he took aim at Krishna, hurting him lightly. Krishna fainted in a preordained, divine plan adopted to empower Satyabhama. Seeing this Satyabhama was furious. She doubled her attack on the demon king and killed him finally. Before Narakasura's death, he requested a boon from his mother, Satyabhama, that everyone should celebrate his death with colorful light. Thus this day is celebrated as the first day of Diwali - 'Naraka Chaturdashi'.
Krishna and Satyabhama's victory on Narakasura translated into freedom for all his prisoners and honoring of Aditi. Having rescued the 16,100 women, Krishna married them to restore them to their former dignity.