Sycorax

The Sycorax are an alien race, that first appeared in The Christmas Invasion. The space probe Guinevere One crashed into a Sycorax spaceship near Mars. The Sycorax's intent was to enslave humanity, using blood magic to force humanity's hand into surrending. Using the blood magic, their apparent leader controlled everyone with the A+ blood type to stand at the edge of any tall structure, just waiting for the command to throw themselves off. The Doctor activated the blood magic and no humans killed themselves; their survival instincts were too strong. The Sycorax were forced to leave Earth and humanity alone after the Doctor defeated their leader in a sword duel. Although the Sycorax ship was leaving, the Prime Minister of the time Harriet Jones ordered Torchwood to fire. Five beams of green light converged over London (a la Death Star) and destroyed the spaceship outright.