Kai Tobias

 was part of a community on Phobos. He told Amy and Farl about the Phobians. He wanted people to no longer travel to Phobos. He told the Eighth Doctor his stories. He enticed people's fears. He created the being that was terrorising the populace. He wanted to kill the Doctor and Lucie Miller by throwing them down the wormhole. (AUDIO: Phobos)