Nyssa was a native of the planet Traken, the capital of the Traken Union. She was acquainted with the Fourth Doctor but was mainly a companion of the Fifth Doctor. She also adventured with Adric, Tegan and briefly Turlough and the Brigadier.
The daughter of Consul Tremas, Nyssa was a child of privilege on Traken. She was gifted with a brilliant intellect and specialised in bioelectronics. When Traken was destroyed, Nyssa became the last of her kind.
Nyssa first met the Doctor in his fourth incarnation when he was travelling with Adric. She was preparing to celebrate the marriage of her long-widowed father to Kassia. Unbeknownst to her, the Master had also come to Traken and was planning to exploit the tremendous power of the Keepership, to which her father was the only rightful heir. One of his purposes was to live beyond his last natural regeneration. The Doctor and Adric stopped the Master from taking over the Keepership, but could not prevent his killing Nyssa's new step-mother. They also did not stop the Master from "killing" Tremas by transferring his essence into Tremas' body. The Master lived and Nyssa was orphaned in her young adulthood.
Nyssa seemed at once more mature and more naive than her fellow travellers. She did not boast of her scientific knowledge nor believe it made her superior. She faced her challenges with the determination and serenity of her Trakenite heritage. She turned her sorrow as the last of her people into a desire to help others. Rarely did she mention any grief she suffered because of her great misfortunes. Perhaps most extraordinarily, she never sought to avenge herself on the Master despite her many good reasons to do so.
Her trusting nature sometimes made her less alert to deception than Tegan, but it also made her more adept at negotiating an effective balance between strong personalities. She had probably the closest relationship with the Fifth Doctor of any of his companions. Nyssa's near-royal upbringing and natural curiosity sometimes made it hard for her to relax and enjoy herself. Though her outlook usually tended to be serious, she displayed a dry wit on occasion, particularly when dealing with the Fifth Doctor's boyish idiosyncrasies.
She tended towards pacifism, though on one occasion she destroyed a Terileptil android and used the threat of violence to save the Doctor's life, shooting a pair of guards.
Even though her world and her people were vanished, she strove to live by their principles. Nyssa was one of the Doctor's most intelligent companions and was one of the few capable of assisting with TARDIS operations.
Nyssa was originally meant to have appeared only in The Keeper of Traken as a supporting character. She was therefore the sole creation of writer Johnny Byrne, to whom royalties had to be paid when the character was used. Like the Brigadier and K9, she is a rare example of a series regular to whom the BBC does not enjoy sole copyright.
