Black hole converter
From Tardis Wiki, the free Doctor Who reference
The Master made use of a black hole converter on board each of his warships. They were created for use in destroying other planets once the Time Lord Empire launched war against the Universe. When he was denied control of Earth, he told the Doctor he would rather destroy it, but was ultimately convinced not to by the Doctor. When time was reversed, the warships and black hole converters disappeared from Earth. (DW: Last of the Time Lords)
