Narakasura was the son of Bhudevi and Lord Varaha (an avatar of Shri Vishnu). However, he grew greedy and unjust. He created destruction and devastation without the fear of death. He knew that as per Lord Brahma’s boon, none other than his mother, Bhudevi could kill him. Therefore, he became complacent. Once he attacked Lord Krishna. And the latter’s consort, Sathyabhama, who was an incarnation of Bhudevi, retaliated with much vigour and courage. She killed Narakasura, thereby sanctifying Brahma’s boon.