Via the BBC:
The Doctor and Clara face their Last Christmas.
Trapped on an Arctic base, under attack from terrifying creatures, who are you going to call? Santa Claus!’ Will this really be the Last Christmas for the Doctor and Clara? And what exactly are these terrifying creatures?
It’s not the first time the Doctor has visited the Arctic of course. It’s previously been home to an Ice Warrior in Cold War - and the Cybermen!
Perhaps there are clues to be found if you watch the teaser for the Christmas episode.
The episode will star Peter Capaldi, Jenna Coleman, Nick Frost, Michael Troughton and Nathan McMullen – along with a host of guest stars.