The "Doctor Who" Christmas special, "The Day of the Doctor," will serve as a sendoff to Matt Smith's run as the 11th Doctor. While BBC has teased plenty, few plot points have been leaked ahead of its Dec. 25 premiere. In newly released promo photos, it is revealed that Tasha Lem, a woman from the Doctor's past, may be part Dalek.

Lem, played by Orla Brady, is an "old friend" of the Doctor but the previously released previews or photos did not reveal much about the character or her motivations in "The Time of the Doctor." Brady herself has remained coy about her role but a new photo from BBC reveals a Dalek eyestalk coming out of Lem's head. If Lem is part Dalek that would certainly add another wrinkle to her relationship with the Doctor.

Tasha Lem
A new promo image from the "Doctor Who" Christmas special reveals Tasha Lem is part Dalek. BBC

A new "The Time of the Doctor" preview features the first extended look at any interaction between Lem, the Doctor and Clara Oswald. While the clip does not feature any plot points it does suggest a lengthy history between the Doctor and Lem, the majority of which cannot be shared in front of Clara.

In the first "The Time of the Doctor" trailer, fans were treated to a look at the lineup of monsters that will threaten the Doctor in the Christmas special. Daleks, Cybermen, Weeping Angels and the Silence will challenge Matt Smith's 11th Doctor, or, technically, the 13th Doctor, for the last time. With the "siege of Trenzalore" taking place during the "Doctor Who" Christmas special, showrunner Stephen Moffat's sendoff for Smith will feature plenty of action but the episode promises to feature some lighthearted moments as fans say goodbye to Smith. The newly released photos include a peek at the "fair bit of nudity" that Moffat promised.

Doctor Who Christmas Special
The "Doctor Who" Christmas Special, "The Time of the Doctor," will be the last episode for Matt Smith. BBC

In another "The Time of the Doctor" preview, Clara is seen scrambling to cook Christmas dinner for her family while asking the Doctor to pose as her boyfriend. Smith's Doctor is a bit preoccupied at the moment and when the TARDIS discovers a new ship, he is off to discover its secrets.

Luckily, fans will not have to wait much longer to watch the "Doctor Who" Christmas special. The episode will be a bittersweet one as Smith ends his time as the Doctor and will mark the beginning of Peter Capaldi's run as the Doctor. "The Time of the Doctor" will air on Dec. 25, on BBC One in the UK at 7:30 p.m. local time and on BBC America at 9 p.m. EST, 8 p.m. CST.