Ultimate Sanction

Proposed by Lord President Rassilon as the last resort to winning the Last Great Time War, the Ultimate Sanction involved the creation of a paradox so severe that the resulting spatial-temporal rupture would rip the Time Vortex apart.

As this would be a suicidal measure, Rassilon then devised a way of allowing the Time Lords to escape the disintegration of Creation by having the whole race shed their corporeal bodies and become creatures of consciousness alone, ones that would escape the effects of time and of cause and effect. (DW: The End of Time)

This plan was thwarted when the Eighth Doctor came into possession of the Moment and used it to not only destroy every last participant of the Last Great Time War (DW: The End of Time), but also to Time-lock the Last Great Time War itself. (DW: The Stolen Earth)

Nevertheless, Rassilon nearly succeeded when his sleeper agent, the Master, used a Whitepoint Star diamond to send a physical rhythmic signal of four beats into time and space. Rassilon then locked onto that signal, using it as a homing beacon to break himself, and Gallifrey (and every other participant of the Last Great Time War), out of the time lock and begin the End of Time.

However, Rassilon was once again foiled when the Tenth Doctor used Wilfred Mott's old service revolver to destroy the White-Point Star, the key component of the signal that allowed the escape from the time lock, and Gallifrey was plunged back into its last day. (DW: The End of Time)

This event was foreseen by the Ood (DW: Planet of the Ood), Carmen (DW: Planet of the Dead) and the Trickster (SJA: The Wedding of Sarah Jane Smith). They all tried to warn the Doctor through prophecies, which also informed him of his upcoming regeneration.

Behind the scenes

 * In DW: The Parting of the Ways, the Ninth Doctor tells Rose and Jack about the Last Great Time War, stating that the whole of creation was at stake, presumably this is what he meant.