Also, the Kalika Purana says Narakasura, the son of Booma Devi and Vishnu-Narayana, brought brahmins and settled them in Kamarupa / Kamakhya. So one starts wondering why would an asura bring brahmins to settle in kamarupa, and why did 'Krishna' kill Narakasura if Narakasura was a follower of the brahmanical religion ??
In Hindu beliefs, Narakasura or Naraka is the asura son of the earth goddess Bhudevi (Bhumi) and Lord Vishnu in his Varaha (boar) Avatar (incarnation). In other sources, he is the son of the asura Hiranyaksha. He 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.
The legend of Narakasura is important in the history of Assam since Narakasura is cited as the progenitor of many dynasties that ruled Kamarupa in historical times. A hill, to the south of Guwahati is named after him. He is also associated with the myth of the shakta goddess and place of worship Kamakhya.Narakasura became evil, in association with another Asura named Banasura. Drunk with power, as he knew himself to be unrivalled 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. Now 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 would attend to this matter, when he would 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 Narakasura's ill treatment of women and his behaviour 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) large army, that he unleashed on Krishna. However, the Lord slew them all with little effort. Krishna also killed Mura, Narakasura's general. Thus Krishna is called 'Mura-ri'(the enemy of Mura). 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. [source:wikipedia]
