In the latest issue of Doctor Who Magazine, no. 468 and out now, Steven Moffat has been chatting about the finale for Matt Smith's Doctor, The Time of the Doctor. Regarding the Doctor Who 2013 Christmas Special, the showrunner says of mysterious character Tasha Lem:
"The Doctor meets an old friend. Someone from his distant past. Someone who knows him very well, but whom we have never met. She's the Mother Superious of the Papal Mainframe."
DWM also adds that the one hour special sees The Doctor helping Clara to cook Christmas Dinner and a "fair bit of nudity." Doctor Who Magazine 468 is out now, complete with two HUGE posters, and available from all good newsagents.