When Bhishma, the great grand uncle of the Kauravas and the Pandavas, refused to marry Amba, she sat in penance and got a boon from Lord Shiva that she would be able to kill Bhishma who himself had the boon of being immortal. In her next birth she was born a man and fought from the side of the Pandavas. Bhishma had sworn never to raise arms on a woman so when he came before him, Bhishma dropped his arms and gave up. Who did Amba take rebirth as?