Zara

Zara was a tracer in human form.

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

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

Zara and Zink would later 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 to the Key to Time. (BFA: The Judgement of Isskar)

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

After escaping the Sphere, she and Abby, formally Amy, are 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 is nearly killed until the angry mob believed that Abby was also killed. (GRC: The Fog)