Paradox machine
From Tardis Wiki, the free Doctor Who reference
The Paradox machine was a type of technology that was capable of creating a tear in space and time.
The Master used such a machine by cannibalising the The Doctor's TARDIS in order to allow his army of Toclafane to invade Earth. The device created a tear in the sky allowing millions of the sphere-like aliens to attack the planet and its populace. (DW: The Sound of Drums)
