Astra of Atrios

Princess Astra of Atrios was the sixth Princess of the sixth dynasty of the sixth royal house of Atrios. Astra was kidnapped by the Shadow and later transmuted to her true shape, a segment of the Key to Time. After the Fourth Doctor 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)''