Denaxian
From Tardis Wiki, the free Doctor Who reference
Denaxians were the most paranoid species in the known universe. They trusted nobody, and their home planet was kept a mystery. Denaxians were totally committed to keeping it hidden. If there was a threat to expose the location of their home world, they sent out a death ship, containing a single assassin to eliminate the threat. (PROSE: How To Appear Human In Several Uneasy Lessons)
