Qurra

Quarra was a female member of the Silurian species who were sometimes known as Earth Reptiles.

At some point in the future, her people were involved in a devastating war over a human colony. This planet had established a base on its moon that possessed a doomsday weapon capable of scouring the colony of all life with such an approach in place just in case the Earth Reptiles won the conflict. To prevent its use, the Silurians dispatched Quarra to infiltrate the moonbase where she managed to eliminate the entire crew from the data she had received. However, she was unaware of an entertainer called Jen Yates present on the base who was not on the crew list. After her comrades were killed, Yates managed to activate the doomsday device just before Quarra killed her.

Life on the colony was wiped out and Quarra was shocked by the turn of events. The sheer nature of the horror she had witnessed as well as the guilt she had felt resulted in the Silurian taking on the personality of Jen Yates. She came to believe that she was the only human occupant of the facility and was guarding it as the war continued the rage against the Earth Reptiles. At that time, she was also guarding a frozen embryo. She eventually encountered the Doctor along with his Companions Ace and Benny Summerfield. Whilst initially happy to meet other people, this "Jen" became suspicious of them when they began to avoid talking about certain subjects and she concluded that they were enemies. In the resultant fight, Ace managed to hold her back whilst The Doctor threatened to destroy one of the frozen embryo's she was guarding. In desperation, she unwittingly used her third eye against the Doctor.

It was then she remembered that she was in fact Quarra, the Earth Reptile sent to infiltrate the colony and the result of her failure. Unable to accept her actions, she walked out of the moonbase without the aid of a spacesuit thus killing herself in the process. (ST: Cold War)