Kitig was a Tractite.
He was from an alternate timeline where humans had never evolved on Earth. When the Eighth Doctor arrived, he learned that he was going to uncreate the timeline. At first he tried to kill the Doctor, but then came to understand that the timeline had to be destroyed to save the universe.
He carved a series of messages in the past to contact Sam Jones and Jo Grant in the future so they could come back and help the Doctor. After he finished, he used the time tree which had created the timeline to travel back to the solar system's beginning. This was so the tree could be destroyed and not misused again. Kitig also died in the vacuum of space, watching the Earth form. (PROSE: Genocide)