|Type:||Time machine, TARDIS|
|Made by:||The Master|
|Appearances:||TV: The Sound of Drums / Last of the Time Lords|
The paradox machine was wrecked by Captain Jack Harkness with an assault rifle. The destruction of the machine reversed time to the moment it was activated, undoing everything that had occurred since then. While those within close range of the machine on the Valiant remembered the timeline, for the rest of the universe it had never happened. (TV: Last of the Time Lords)
The interior of the paradox machine was lit by an ominous red glow. Whilst it was active, the cloister bell sounded continually. The belligerent destruction the Master had wreaked upon the TARDIS activated the bell, a ceaseless warning that the TARDIS, and perhaps the fabric of time itself, were threatened by the paradox machine as long as it remained operational.
The main console in particular had undergone many modifications by the Master: the console itself was enclosed inside a metal cage, with tubes and appendages attached to it. At its base was a pipe connecting to another area of the TARDIS, with a dial showing a readout of the pressure build-up inside. It shot out puffs of steam when it was activated.
- The Doctor claimed that he could have used the TARDIS to sustain a paradox of two different temporal versions of Amy Pond simultaneously aboard the TARDIS at once - he initially said it was possible if he disabled some of the TARDIS' peripheral functions and "jettisoned the karaoke bar". Because this turned out to be a lie, it's unknown precisely what potential for similar paradox prevention features the TARDIS has. (TV: The Girl Who Waited)