Joxer
From Tardis Wiki, the free Doctor Who reference
Joxer was an alien who came to Earth in 1791 to find slaves. He shared a body with Hempel. He suggested the extermination of the humans to increase the price at which they could sell the slaves. After seeing that the Tenth Doctor was a superior lifeform, he obeyed his commands and released all of the slaves. (AUDIO: The Sword of the Chevalier)
