In the movie Doctor Who: The Time of the Doctor, the Doctor and Clara travel to a planet where many dangerous species are converging, drawn by a mysterious message that has been echoing throughout the universe. The Doctor realizes that the message is coming from a planet called Trenzalore, and that it is the signal for the end of his life.
On Trenzalore, the Doctor discovers that a powerful entity called the Time Lords is trying to return to the universe, and that they are using the message to find their way back. However, the Time Lords are also being pursued by the Daleks, who are determined to destroy them once and for all.
As the battle between the Time Lords and the Daleks rages on, the Doctor learns that the message is actually coming from his own timeline, and that he is the one responsible for sending it. He realizes that he must stay on Trenzalore and protect the planet from the Daleks, even if it means sacrificing his own life.
In the end, the Doctor is able to save Trenzalore and the Time Lords, but at a great cost. He regenerates into a new incarnation, and Clara is left to deal with the loss of her friend and the arrival of a new face.