AceShowbiz -

A new trailer for the upcoming "Doctor Who" Christmas special called "The Time of The Doctor", which will be the final episode of Matt Smith, has landed online. Sharing more footage, the video prepares fans for a farewell to the 11th incarnation of the Doctor.

"Everything ends, Clara," the doctor tells his companion and best friend, Clara, "and sooner than you think." Teasing the return of the doctor's old enemies, the extended preview also features Orla Brady as mysterious villainess Tasha Lem, who declares, "The Time War will begin anew. The siege of Trenzalore has now begun."

An official synopsis of the episode reads, "Orbiting a quiet backwater planet, the massed forces of the universe's deadliest species gather, drawn to a mysterious message that echoes out to the stars. And amongst them - the Doctor. Rescuing Clara from a family Christmas dinner, the Time Lord and his best friend must learn what this enigmatic signal means for his own fate and that of the universe."

Showrunner Steven Moffat said of Smith's final episode, "It's a moment of huge sadness but it doesn't end there. It's an insane emotional reversal, and that's what Doctor Who is made of." The episode will introduce Peter Capaldi as the 12th doctor.