Cyrian

Cyrian was a young man who, while stranded on the planet DV Acrol 8 and being pursued by Cybermen, was rescued by the Rani, who took him aboard her TARDIS to become her travelling companion. (PROSE: Rescue) He assisted her in her plot to trap various incarnations of the Doctor. (TV: Dimensions in Time)


 * Since First Frontier established that the events of Dimensions in Time only took place in the Seventh Doctor's dream, it seems likely that Cyrian is likewise also a dream character, unless he was based on someone the Doctor had previously met.