Ultimate Sanction

The Final Sanction, also known as the Ultimate Sanction, was a plan instigated by the Time Lords during the last years of the Last Great Time War. It was spearheaded by the Lord President Rassilon himself and involved causing a rip within the Time Vortex itself which was an act considered suicidal. However, it was believed that this would allow the inhabitants of Gallifrey to ascend into beings of pure consciousness thus free of flesh as well as of time. This act, however, would lead to the destruction of both Time and all of creation itself. They were prevented from accomplishing this act as a result of the Last Great Time War.

Through The Master during his time as Harold Saxon, Rassilon managed to allow the Time Lords and Gallifrey to escape the Time-lock surrounding the war in order to complete the Ultimate Sanction. However, they were prevented from doing so by the Doctor who sent them back into the Time-lock thus preventing the horrors they would unleash on the universe. (DW: The End of Time)