Skovox Blitzer

A Skovox Blitzer was a robot built for war, said to be among the most dangerous weapons ever created. A single Blitzer contained enough armament to destroy a planet. One came to Earth in the early 21st century, attracted to the area around Coal Hill School by the high number of artron energy emissions. It was detected by the Twelfth Doctor, who trapped it and projected it into the Time Vortex by using chronodyne generators.

However, as Danny Pink had turned off some of the generators, it was not projected as far into the future as the Doctor had planned. Before it reappeared, he developed a device that would make his orders sound as though they were coming from one of the robot's superiors. With the assistance of Clara Oswald and Danny, he again trapped it, and ordered it to deactivate. He then left it drifting in space. (TV: The Caretaker)

Behind The Scenes
.The Blitzer's voice was originally very erratic sounding, constantly shifting in pitch. The voice was later dubbed over by a deeper, more consistent sound. Not much is known why the original voice was changed, although rumours suggest that it was because it was difficult to understand. The original voice can be briefly heard in the next time trailer however.