- Bhisma begins telling the story of Amba/Sikhandin-- the only person, barring the Pandavas, whom he will not fight in the coming battle. The reason for this is that Sikhandin had once been a female. She was not just any female at that-- she was Draupadi's sister, and in her past life, she'd had a bad run-in with Bhisma, making her his sworn enemy from beyond the grave.
We begin the story with Amba's abduction, along with her sisters Ambika and Ambalika, by Bhisma to provide wives for his brother. When she announces her pre-arranged betrothal with Shalva, she is freed to go to him. A comedy of errors ensues when he questions her virtue, and then she breaks from her escort, ruining her reputation. But this is a deadly serious matter. The girl is now unmarriageable, and her father would be unlikely to take her back. She has died to her caste and is possibly the most vulnerable person in all of India.
Amba seeks shelter with the Brahmins & ascetics, and finally enlists Rama Jamadagni as her champion. Bhisma is too stubborn to even allow his own guru to make him take a woman of questionable virtue into his house, so Rama kills him. Bhisma has a near-death experience and is reminded of his past existence as one of the divine Vasus, and discovers that his holy brothers are still looking out for him.
Bhisma cannot die now, because his appointment with Destiny has already been set with the incarnation of the Primeval God, Nara Prajapati-- Arjuna Kaunteya.