Amba was a princess of the Kashi kingdom who was abducted by Bhishma, a respected warrior and patriarch of the Kuru dynasty. Bhishma had kidnapped Amba and her sisters to be married to his half-brother Vichitravirya, who was the king of Hastinapur. However, Amba was in love with another prince and refused to marry Vichitravirya.
Bhishma, bound by his vow of celibacy, was unable to marry Amba himself or allow her to marry someone else. He eventually sent Amba back to her kingdom, but she was rejected by her family because she was no longer a virgin after having been abducted. Amba was left alone and without any prospects for marriage or support.
Feeling betrayed and vengeful, Amba went to various kings seeking help to take revenge on Bhishma. She eventually found a powerful warrior named Parasurama who agreed to train her and give her weapons to fight against Bhishma.
Amba returned to the battlefield and challenged Bhishma to a duel, but Bhishma refused to fight a woman. Amba then invoked the gods to give her a male body so that she could fight Bhishma, and her wish was granted. She became Shikhandi, a male warrior who fought alongside the Pandavas in the Kurukshetra War.
In the final battle of the Kurukshetra War, Shikhandi was instrumental in the death of Bhishma. Bhishma, recognizing Shikhandi as Amba, did not fight back against him/her because he felt guilty for his actions towards her. Shikhandi shot Bhishma with arrows, and he fell from his chariot and was mortally wounded.
After Bhishma’s death, Shikhandi returned to her female form and retired to a life of penance and meditation. The story of Amba/Shikhandi is a complex one that touches on themes of gender, power, and revenge in the Mahabharata.