Satyabhama is the third wife of Lord Krishna, known for her strong will and tantrums. She is believed to be a partial avatar of Bhudevi.
Satyabhama was the daughter of Satrajit who owned the Syamantaka jewel. Satrajit, who secured the jewel from Surya, and would not part with it even when Lord Krishna the king of Dwarka, asked for it saying it would be safe with him. Shortly thereafter, Prasena, the brother of Satrajit went out hunting wearing the jewel but was killed by a lion. Jambavan, known for his role in the Ramayana, killed the lion and gave the jewel to his daughter to play with. When Prasena did not return, Satrajit falsely accused Krishna of killing Prasena for the sake of the jewel.
Krishna, in order to remove the stain on his reputation, set out in search of the jewel and found it in Jambavan's cave, with his child. Jambavan attacked Krishna thinking him to be an intruder who had come to take away the jewel. They fought each other for 28 days, when Jambavan, his whole body terribly weakened from the hammering of Krishna's fists, finally recognised Him as Rama and surrendered.
As repentance for his having fought Krishna, Jambavan gave Krishna the jewel and also his daughter Jambavati in marriage. Krishna returned the jewel to Satrajit, who in turn repented for his false accusation. He promptly offered to give Krishna the jewel and his daughter Satyabhama in marriage. Krishna accepted Satyabhama as His wife but did not accept the jewel. 
Narakasura was a demon king, ruling Pragjothishyapur, the present day Assam. He gained a boon from Brahma that he would die only in the hands of his mother. Armed with the boon, he ruled like a despot. Narakasura was infamous for his wicked ruling and high disregard for demigods and women. His mother was Bhoomi Devi. Also his mother had obtained a boon from Lord Vishnu that her Son should die only when she wishes for.