The Skin of the Sleek (Marc Platt)

 Name: Sartiacaradinora, known as 'Sartia' for short

 Format: Audio

 Time of Origin: Gallifrey, in the same class as Romana 1

 Appearances: "The Skin of the Sleek/The Thief Who Stole Time"

 Doctor: Fourth Doctor

 Companions: Romana 2; attending the Academy with Romana 1; K9 was in the TARDIS but did not encounter Sartia directly.

 History: A Time Lady who attended the academy with The Doctor's future companion Romanadvoratrelundar, Sartiacaradinora - known to others as 'Sartia' for short - can almost be seen as Romana's equivalent of The Master, as an old friend turned to villainy out of a desire for power where Romana simply wanted to see the wider universe. However, Sartia differs from The Master in two key ways; not only has Sartia only made one appearance in contrast to The Master's recurring confrontations, but in her only depicted appearance she was fundamentally defeated by her own incompetence, trying to control a power she couldn't understand where The Master is generally more cautious about trying to seek out greater powers for his own benefit.

 Back when Romana and Sartia were at the Academy, they were apparently part of the same study group, but where Romana considered Sartia her best friend Sartia later claimed that she and the other students would chastise Romana for being an overachieving teacher's pet. Dismissing the Academy as teaching nothing but 'boring theory', Sartia began to search Gallifrey's records for a chance to gain greater power for herself. Finding records of a planet called Funderell, which the Time Lords had gone out of their way to hide, Sartia concluded that there was some kind of ancient treasure buried there, stealing a time ring and a taser so that she could set out to find it for herself.

 Having left Gallifrey, Sartia infiltrated a documentary crew headed by Eamonn Orensky that was heading for Funderell, defined as a grade 3 planet that had been officially off-limits for over 46 thousand years, apparently once protected by transduction barriers that had degraded long ago. By this point, the planet was inhabited by only a small colony and mostly consisted of thick green water, to the extent that the only solid surface on the planet was a floating town; while it was theoretically possible to walk along the water, anything that remained still would start to sink. Aside from the humanoid colony, the only native life form were the Sleek, essentially giant electric eels. The colony was 'led' by a Soothsayer, who was chained to a book that would allow them to record the future they perceived, with the duty passed from father to son when the previous soothsayer became too old, the son generally allowed to remain 'free' just long enough to have their own child before they were chained to the book.

The Fourth Doctor

 After Orensky's crew crashed onto the planet's surface, they made contact with the natives and recorded footage of their activities while waiting for a rescue team to come for them. Eventually, the Fourth Doctor arrived on Funderell accompanied by Romana, now in her second incarnation. While The Doctor made contact with Orensky's documentary crew while he and Romana were separated on the planet, he identified Sartia as a Time Lord, but she obviously avoided revealing her real reason for being on the planet. When Sartia went to retrieve Romana from the nearby village, the situation became complicated when the locals decided to sacrifice them to their god, Funderell's daughter, a giant Sleek. Sartia killed the Sleek with her staser and forced Romana to help her translate the writings she had found discussing Funderell's true nature, subsequently dumping Romana in the planet's gelatinous sea while revealing her old resentment of Romana.

The Thief Who Stole Time (Marc Platt)

 With Romana's translated notes, Sartia determined that Funderell was located at a nexus of parallel timelines, with the planet having been engineered by the Time Lords to serve as a 'plug' to stabilise 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 with the Soothsayers, and the Time Lords themselves forgot about the planet. Upon making this discovery, Sartia killed the ship's pilot, Klick Chervain, after he refused to aid her in her plans, then came into possession of another Gallifreyan artefact, an orb which would allow her to directly control the parallel timelines.

 While Romana had been rescued by The Doctor and returned to the TARDIS, Sartia forced Romana to let her in by creating the illusion of timelines where The Doctor was in danger so that Romana would be compelled to open the door. Sartia attempted to connect the orb to the TARDIS, reasoning that both were old enough to be potentially compatible with each other, hoping that she could combine their power to essentially make herself a god. However, this led to multiple timelines becoming entangled, driving Sartia insane from the strain of all that knowledge being forced into her mind, leaving her ranting in anger at Romana until she was finally knocked out after The Doctor was able to access a long-buried external control unit for Funderell that 'reset' the planet to a more stable environment. When Sartia recovered, after her staser was lost, she used her Time Ring to escape. Despite her anger at Romana and her expressed ambitions for personal power, Sartia hasn't been seen since, suggesting that her ego outweighed her abilities and she was ultimately killed during her later travels through the wider universe.