Zara

Zara, later Joy, was a tracer in human form.

Biography
Zara was created by the Grace, powerful beings who created the Key to Time, to prevent the completion of the Key. Like her twin sister, Amy, she existed to find the segments of the Key to Time. (AUDIO: The Judgement of Isskar)

During her journey, Zara was taken prisoner with the Seventh Doctor's companion Ace on the planet of Erratoon. She escaped with the help of Harmonious 14 Zink. (AUDIO: The Prisoner's Dilemma)

Zara and Zink would encounter the Fifth Doctor and, her twin sister, Amy on the planet Mars. Zara would soon cause the collapse of the Martian society after finding a segment of the Key to Time. (AUDIO: The Judgement of Isskar)

After being freed by the Grace, Zara made her way to the Sphere. On the Sphere, Zara met Marek, who got her pregnant. (AUDIO: The Sphere)

After escaping the Sphere, Abby, formerly Amy, and she were taken into custody and accused of killing the loved ones of the people from a mysterious village called Compton. During an escape attempt Zara was left behind in their jail cell. Zara was threatened with death until the angry mob believed that Abby was also killed. (AUDIO: The Fog)