Nessican

Nessican was a vampire-like humanoid assassin who, with his partner Cain, was sent to Earth by Tannis to kill Valentine and Antenor - Time Lords known as 'The Saints' and members of the Fraction. He had escaped from a prison planet and had no intention of returning, but was poisoned in the London sewers after drinking the blood of the Doctor who had just eaten garlic. (WC: Death Comes to Time)