Karadax (planet)

Karadax was a planet inhabited by a bipedal shark species, also called the Karadax. When the Tenth Doctor and Martha first went to Karadax, and a Karadax came back in time to try to kill Martha, because without her the Doctor would be unable to stop their future plans. He failed, and the Doctor decided to check up on Karadax every few hundred years. (PROSE: Rewriting History)