As the head scientist, Tryana contributed to the Thal's continued development after the initial defeat of the Daleks. Despite this, she remained cautious of the direction the Thals were heading and advocated a return to their pacifist ways.
She was one of few Thals allowed access into the Dalek City for purposes of scientific research. On one excursion, she discovered a secret level beneath the rest of the city and encountered Dalek survivors. Among them was the Dalek Supreme who appealed to her desire to rebuild Skaro and manipulated her into aiding them.
Tryana supplied the Daleks with power from the Thal City and in return, the Daleks provided her with resources to make improvements to the Thal City and to construct ionisation towers that could combat the radiation in the atmosphere. Tryana believed the Daleks had reformed that held truly benevolent intentions but kept her encounters secret from the rest of her people.
Tryana accompanied the First Doctor, Ian Chesterton and Kreos' soldiers to the Dalek City when Jyden and Susan Foreman embarked on an unauthorised exploration. There, her secrets were exposed but the Daleks asked that they be allowed to appeal to the Thal's High Leader, Damadus. This opened the door for a full-scale Dalek attack on the Thal City. At this revelation, Tryana confronted the Dalek Supreme but she was killed on the spot after outliving her usefulness.
Jyden refused to believe his mother would ever have helped the Daleks. He and Ian raided the Dalek City to rescue the Doctor and Susan, where he learned Tryana had been killed. (AUDIO: Return to Skaro)