A small device, easy to carry, the Time Destructor would only work once, exhausting its taranium core. It could accelerate or reverse the flow of time with devastating effect. It was controlled by a switch. The Doctor's TARDIS offered immunity from the distortions to the time flow. Once the Time Destructor had burnt itself out, its effects reversed for the survivors, though not for those killed by it. (TV: The Daleks' Master Plan)