Astra of Atrios

Princess Astra of Atrios Royal Princess of Atrios who turned out to be the sixth segment to The Key to Time. She 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. After the Fourth Doctor defiled 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. The Armageddon Factor

Soon afterwards, Romana decided to regenerate and eventually adopted Princess Astra's shape Destiny of the Daleks