Varn (The Invasion of Time)

Varn
Species:	Time Lord
Job:	Bodyguard
Affiliated with:	Chancellery Guard
Place of origin:	Gallifrey
Appearance:	The Invasion of Time
Main actor:	Michael Harley

You may be looking for the Sontaran or the Dominator.

Varn was commander of Castellan Kelner's bodyguard. Kelner ordered him to protect the Fourth Doctor at all times and report back with everything the Doctor said or did. (PROSE: Doctor Who and the Invasion of Time) He understood the extent of Kelner's plotting and knew he would be rewarded if he agreed. He was shot and killed by Andred. (TV: The Invasion of Time)