Terminators are Space Marine or Adeptus Custodes veterans who have earned the right to wear Terminator armor through exemplary service. But of course you came here because of Space Marines in Terminator armour. It's also the name of a franchise that began in 984.M2 based on a type of robot employed by the A.I Skynet for its noble goal of cleaning Earth of human scum (initially humanoid infiltrator type - which a certain race of robots in 40k is based on, but later all Skynet robots came to be called that). Terminator is the border between day and night sides of the planet, also known as a 'twilight zone'. 'If I am to die, I DIE STANDING!' – Dawn of War 2 Terminators, exemplifying the average tenacity of the Chapter's finest.