Mran'ofet was a Martian in an alternate timeline.
Jack Kowaczski was very fond of the servant Sio'phut. When he invented his time machine, he travelled to ancient Mars to warn them of Earth's eventual invasion. However, the thin atmosphere caused his death shortly after arriving. Millions of other versions of Jack from other timelines did the same thing. The decaying bodies paradoxically led to the creation of the Martian species.
Mran'ofet told this story to several versions of Jack. Knowing their "entire civilisation was based on a pyramid of impossibilities", they did not oppose the Eighth Doctor preventing the initial paradox, which they knew would cause them to cease to exist. (PROSE: The Last Resort)