Darius Kieran Cheynor was a member of the Terran Survey Corps and descendant of Tom Cheynor.

When he first met the Seventh Doctor and Bernice Summerfield, he was a lieutenant-commander and second officer on the Survey Ship Icarus. He was part of the Garvond's plan to completely manifest in the universe, which was stopped by the Doctor. (PROSE: The Dimension Riders)

Later, as a captain, he encountered the Doctor and Benny again while he was fighting the Phractons on Gadrell Major. He joined the Phractons to stop the Sensopath Shanstra. After she was killed, there were still militants amongst the Phractons who wanted to fight the humans. A shuttle explosion which killed Cheynor and Suzi Palsson mollified them, as they blamed Cheynor for the death of their Commander on Gadrell Major. The Doctor could not prevent their deaths as they were part of history. (PROSE: Infinite Requiem)