Along with her sisters Ambika and Ambalika, she was taken by force by Bhishma from their Swayamvara. (Bhishma challenged the assembled Kings and Princes and defeated them.) He presented them to Satyavati for marriage to Vichitravirya, the king of Hastinapura.
Vichitravirya married only her sisters and rejected Amba since she had already given her heart to another. When Amba went to see her beloved, he rejected her as well in shame of losing the combat against Bhishma at the Swayamvara. Amba then returned to Bhishma and demanded that he marry her. He declined since he had already taken a vow of bachelorhood. Enraged that she was going to be an unmarriageable women, she swore to kill him, at least in her next life, and died.
She was re-born as Shikhandi the son of Drupada. In the battle of Kurukshetra, Shikhandi was instrumental in Bhishma's death.