Amba was re-born as Shikhandi, the son of Drupada who was also known as Yajnasena, the king of Panchala. Shikhandi was originally born as a girl child named 'Shikhandini. In this birth she had perfect recollection of her previous life as Amba. Shikhandi fought in the Kurukshetra war on the side of the Pandavas, along with his father Drupada and brother Dhristadyumna.

From her birth, a Divine voice told her father to raise her as a son. So Shikhandini was raised like a man, trained in warfare and eventually married. The child was brought up as a boy in all respects. One day while playing near the palace gates, Shikhandini saw a garland of never fading lotuses. This was the garland she had left there in her previous birth as Amba. Shikhandini put the garland round her neck. This was in accordance with the boon given to Amba that the wearer of the garland would cause Bhishma's death.

Right through Shikhandini's childhood the king and queen maintained complete faith in the prophecy of Lord Shiva that though the child was born a female, she would eventually become a male. Therefore they arranged the marriage of Shikhandini with the daughter of king Hiranyavarma of Dasharna. On wedding night, Shikhandi's wife came to know the truth about her husband to be a woman and left Shikhandi to complain the truth to her father. The entire episode infuriated the king Hiranyavarma, who felt cheated and humiliated. He decided to invade Panchala kingdom and kill king Drupada. Drupada, maintaining his full faith in Lord Shiva's prediction, insisted that his son was a male and invited king Hiranyavarma to send some of his courtesans to spend a night with Shikhandini and report on the truth of the matter. Hiranyavarma agreed.

Shikhandini realising that she was the cause of this trouble decided to go the forest and end her life. Shikhansi fled Panchala, but was saved by a Yaksha named Sthunakarna who exchanged his sex with Shikhandi. Shikhandini, who became a man now, went back to Panchala with the name 'Shikhandi' and led a happy married life with his wife and children. After his death, his masculinity was transferred back to the Yaksha.

Shikhandi now in the prime of his youth, learnt the art of warfare from Dronacharya and in due course became great warrior. His sister Draupadi married the five Pandavas. Together with his brother Drishtdyumna, Shikhandi was a source of constant encouragement to the Pandavas against the injustices to them and the humiliation of Draupadi at the hands of the Kauravas.

In the Mahabharata war Shikhandi became one of the seven commanders of the Pandava army. For nine days the battle raged furiously without any side gaining the upper hand. Bhishma was fighting on the Kaurava side but was known to be partial to the Pandavas. After battle on the ninth day he proclaimed that next day either he would kill one of the Pandavas or die fighting. This was the cue for Yudhishthir to ask him how his death could be brought about. Bhishma replied that he would not fight against a woman. When Yudhishthir said that there were no women in the battlefield, Bhishma told him to take Krishna's advice.

Next day Krishna asked Shikhandi to confront Bhishma on the battlefield of Kurukshetra. Bhishma recognised Shikhandi as Amba reborn, and not wanting to fight 'a woman', lowered his weapons. Knowing that Bhishma would react thus to Shikhandi, Arjuna hid behind Shikhandi and attacked Bhishma with a devastating volley of arrows. Thus, only with Shikhandi's help could Arjuna deal a death blow to Bhishma, who had been virtually invincible until then.

Shikhandi was finally killed by Ashwatthama on the 18th day of battle. After the war, when the victorious Pandava army was sleeping in their tents, Ashwatthama, a surviving Kaurava commander, beheaded Shikhandi,Drishtadyumna along with Draupadi's sons.

When Amba was reincarnated, she became a woman again. It is her strong desire in her previous birth as Amba to become the cause of Bheeshma's death and fate of events which made Shikhandini to become a man Shikhandi later enabling Shikhandi to take part in Mahabharata war, ultimately becoming the cause of Bheeshma's death.

The strong desire at the time of death, makes a Soul to reincarnate at a location where it can fulfill its desires and also make it possible to remember the previous birth.

Gender change and even species change is possible in rebirth, so as to fulfill their desires and as per laws of karma.