Fisher King

The Fisher King was an alien warlord who conquered Tivoli and ruled it for ten years. However, the planet was eventually liberated by the Arcateenians. He apparently died and his body was transported to Earth by the Tivolian Prentis. However he was still alive and planned for his people to recover him. He was tricked by the Twelfth Doctor, who blew up a dam. The Fisher King was caught in the flood and killed.