Android Assassin

An Android Assassin was an android that could turn invisible, except for some abnormalities in the air when it moved around. They had disintegrator blasters for assassinating their enemies.

During one of his adventures, fifteen android assassins attacked the Doctor, but he used the energy from their blasters to charge a teleport device via his sonic screwdriver and teleport away in nano-seconds before he was disintegrated. (TV: The Witch's Familiar)