Nova (Sphere of Freedom)

Nova was a human who was briefly a companion of the Ninth Doctor in an aborted timeline.

Biography
Nova was a chef on the Sphere of Freedom who worked for Audrey Mohinson's immersive reality gaming empire. As an eleventh-generation human refugee, she had never heard of Earth and took the opportunity for indenture on the Sphere to find work, but was forced to work fourteen-hour days for no pay other than some food, cramped sleeping quarters, and access to cheap games. As a result of her poor work and upbringing on science fiction, she longed to get away.

Original timeline
Nova met the Ninth Doctor on her way to work while he was tracking down the cause of time eddies. She was highly suspicious of him but eventually allowed him to access the Sphere's central arc on the promise that he could help her escape, where they learnt how the eddies were being fed into the planet's most exclusive game, Ravagers. Three weeks later, the Doctor reappeared and she helped him activate a device that would shut the central arc down, but just as she escaped back to the TARDIS, the time eddies reappeared and she was captured by one. (AUDIO: Sphere of Freedom)

She landed on a planet of giant plants where she encountered flying drones who wanted to wipe her brain and use her as biodegradable fuel, although she was eventually rescued by the Doctor and left to face up to Audrey in person. However, when they arrived, they discovered that the time eddies were out of control and the Ravagers that they were holding back were loose, causing the implosion of the universe. Nova and the Doctor escaped and landed on Tarlishia where they met a much younger Audrey and learnt about her plan, and after being briefly imprisoned, Nova helped the Doctor come up with a plan to use the drones to destroy the offending time particles. (AUDIO: Cataclysm)

With Nova teaming up with the Doctor's recent allies, Captain Halloran, Lieutenant Farraday, and Marcus Aurelius Gallius, they escaped Audrey's guards on the Sphere of Freedom as the Doctor was captured. As Marcus caused a distraction, Nova activated the leftover drones in the TARDIS and used them to destroy the time particles as the Doctor wished, but the time eddies continued to surge, capturing the Doctor in the process. With the Ravagers multiplying and the Doctor gone, Nova simply hoped he could still help them. (AUDIO: Food Fight)

Rebooted timeline
In a new timeline caused by the Doctor accidentally crossing over his history after learning in the time eddy about Audrey's true plans to satiate the Ravagers' hunger and how the Ravagers survive, Nova's first meeting with the Doctor played out slightly differently. The Doctor instead asked Nova some questions about her heritage, but she remained unconvinced of him and left as the Doctor teamed up with Audrey to stop the Ravagers. The Doctor later convinced Audrey to gift Nova enough credits to start a new life on her own, as she explained to the Doctor in a café after the Ravagers were quelled. While there, he explained the adventures he had with her in the original timeline and promised her one trip in the TARDIS with him. (AUDIO: Food Fight)