Shepherd and Shepherdess

 were a pair of beings who could travel between universes destroying them in their wake. They didn't care for the small beings. They came to the Seventh Doctor's universe during World War II in Nazi Germany. They explored Dusseldorf, and it made them said. They gave Kurt Schalk the ideas for the Persuasion machine, so that they could remodel the universe in their image. They absorbed people to feed their hunger and only left ashes. The Seventh Doctor tried to stop them from being evil, by showing them the most beautiful planet in existence, but tricked them onto living on a prison planet. (AUDIO: Persuasion)