10 Most Powerful Weapons In Doctor Who History

Time travel in the Doctor Who universe comes with some rules that cannot be broken. The Doctor can't muck around with "fixed points in time," and visiting your own timestream is frowned upon, though it does happen. It's also very dangerous to alter history in a way that creates a paradox.

Paradoxes can destroy reality itself, so the Doctor is keen on avoiding them wherever possible. The Master is also keenly aware of the danger of paradoxes, which is why he stole the Doctor's TARDIS and converted it into a Paradox Machine when he used the Toclafane to wreak havoc in the present.

The Toclafane are the distant relatives of humanity, who come from beyond the year 100 trillion. They were used to wantonly kill the humans of Earth, which, ordinarily, would have created a paradox, as the Toclafane were descended from them. But thanks to the Paradox Machine, it all worked out fine for the Master. He even did a little dance.

The ability to nullify a paradox makes the Paradox Machine one of the most dangerous weapons in Doctor Who. It wiped away any concerns that could've undone the Master's plan, and it was so volatile that attempting to deactivate or destroy it could've destroyed our solar system.