Cyrian

Cyrian was a young man who came from the asteroid Gaveston. When his spaceship crashed and he became stranded on the planet DV Acrol 8. Pursued by Cybermen, he was rescued by who took him aboard her TARDIS to become her travelling companion. (PROSE: Rescue)

Behind the Scenes
Cyrian was actually first introduced in the 1993 television story NOTVALID: Dimensions in Time. While Rescue is a prequel to this story, this wiki has decided that this aspect does not make both stories invalid.

The name "Cyrian" is an edited version of the pronunciation of "Sir Ian", referencing the originally intended actor Sir Ian McKellen.