The Doctor discovered his grave was located on the planet Trenzalore which he was forced to visit to save his friends the Paternoster Gang. After an image of River Song spoke his name to the enlarged TARDIS, allowing entry, the Doctor and company located his time stream, left when a Time Lord dies in his final form. The entry of the Great Intelligence threatened to remove the Doctor from history until Clara Oswald selflessly jumped in to save him, thereby explaining why the Doctor had met the impossible girl so many times throughout his adventures. The time stream also revealed one of the Doctor's greatest secrets, the War Doctor.