RATS

A Reactive Automated Trail Seeker, also known as , was a rudimentary artificial intelligence which was semi-alive. They were scavengers, often found near war zones to make off with valuable technology. They were programmed to fit in with their surroundings, and had the ability to metamorphose their hands into energy weapons which turned all they touched to antimatter. They spoke in metallic voices, and were programmed to be clearly understood, which led to them listing synonyms for the final word in their sentences.

In London, 1939 a RATS attacked Hetty Warner, believing she had a Gallifreyan stone, fallout of the Last Great Time War, which they had been tracking. However, the Ninth Doctor saved her by attracting its attention with his sonic screwdriver and running off. The next day, a group of eight RATS surrounded the Doctor and Warner, but abandoned them in order to track their primary target- the stone, which the Doctor had activated remotely with his screwdriver. (AUDIO: The Oncoming Storm)