From EmpireOnline: The following is both complete conjecture and a possible spoiler for The Hobbit: There And Back Again, so please think carefully before continuing. But when we spoke to Benedict Cumberbatch on set of Sherlock a little while back, we asked him about his roles in Peter Jackson’s new epic, and he said something that may very well be a spoiler, so let’s discuss that just a bit.
Cumberbatch said of his role,
“I’m playing Smaug through motion-capture and voicing the Necromancer, which is a character in the !!SPOILERS!! Highlight to Read Five Legions War or something which I’m meant to understand. He’s not actually in the original Hobbit. It’s something [Peter Jackson]’s taken from Lord Of The Rings that he wants to put in there.”