Chronon mine

Chronon mines were a type of mine which were used as a weapon during the Last Great Time War, possessing the ability to send their targets back in time. One such mine, referred to as a "stray bullet", was recovered by the Eighth Doctor while he was clearing up the war's "mess". He attached it to the engines of a Sanukuma SporeShip, blasting it back through time and thus returning the Sanukuma back to the beginnings of the universe. (AUDIO: The Rulers of the Universe)