Astra of Atrios

Princess Astra of Atrios was the sixth segment of the Key to Time.

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As the Princess, she was of the sixth dynasty of the sixth royal house of Atrios. Astra was kidnapped by the Shadow and taken to the Shadow's Planet of Evil. She was later transmuted to her true shape. After the Doctor had defeated the Black Guardian and the White Guardian had used the Key to restore universal balance, Princess Astra was restored to her human form and returned to normal life, ruling her planet and presumably marrying Merak. (DW: The Armageddon Factor)

Soon after Astra was restored, the Doctor's companion, Romana, regenerated and chose as her final form the appearance of Astra. (DW: Destiny of the Daleks)''