Sartia

Sartia was a renegade Prydonian Time Lady who attended the Time Lord Academy on Gallifrey with Romana. During her days at the academy, she acted as Romana's friend, but behind her back she and the other students would chastise her for being an overachiever and a tutor's pet. After Romana left the academy, Sartia discovered some ancient records regarding a planet called Fundrell, which the Time Lords had once gone out of their way to hide. Presuming that some sort of ancient treasure lay buried there, she stole a Time Ring and left Gallifrey. After her departure from her homeworld, she joined a documentary crew bound for Fundrell headed up by Eamonn Orensky. They ended up crash-landing on the planet's surface, making contact with the natives and capturing footage of them while they waited for a rescue team to come fetch them.

When the Fourth Doctor and Romana arrived on Fundrell, the Doctor immediately recognized Sartia as a fellow Time Lord. She was sent to fetch Romana, who was separated from the Doctor, from a nearby village, but their reunion was cut short when the locals decided to sacrifice them to their god, Fundrell's Daughter, a giant Sleek. Sartia killed Fundrell's Daughter in self-defense using her staser as she and Romana fled back to the ship. On the ship, Romana and Sartia attempted to decrypt the ancient Gallifreyan text to figure out the nature of Fundrell. (AUDIO: The Skin of the Sleek)

After Sartia attempted to abandon Romana in the gelatinous sea that the planet is composed of, she discovered that Fundrell was located at a nexus of parallel timelines and the planet itself was engineered by the Time Lords to serve as a "plug" to stabilize these parallel timelines. The people of the planet were left there to perform rituals using an ancient Gallifreyan tome in order to maintain the seal that was placed on the planet, but over time the rituals were forgotten and devolved into future-reading rituals and the Time Lords themselves forgot about the planet. Upon making this discovery, Sartia came into possession of another Gallifreyan artifact, an orb which gave her the ability to directly control the parallel timelines. She attempted to use this orb in conjunction with the Doctor's TARDIS to make herself a god, this proved to be dangerous, as array of timelines were tangled. In the end Sartia is knocked out from a jolt of energy resulting from the Doctor and Blujaw Skaldson "rebooting" the planet. When Sartia came to, she attempted to shoot the Doctor and Romana, only to have her staser knocked away by one of Orensky's flying cameras. She then proceeded to use her Time Ring to escape. (AUDIO: ''The Thief Who Stole Time)