Sherlock actor Mark Gatiss has a role in the fourth season of HBO’s Game of Thrones, but, of course, who he will play is still a mystery.

The casting news was first revealed by Entertainment Weekly. Gatiss is a major player in two top British shows - Doctor Who and Sherlock.

He’s written episodes and novels for Doctor Who and has appeared in a few episodes of the show, which is celebrating its 50th anniversary this year. As for Sherlock, he plays Sherlock Holmes’ mysterious brother Mycroft. Uproxx notes that he is also credited as the co-creator of Sherlock with Stephen Moffat.

Showrunners David Benioff and Dan Weiss refused to let EW know who Gatiss is playing, but fans of the show will likely hear some major announcements soon. The Game of Thrones Comic-Con panel is on Friday. Sherlock also has a panel on Thursday.

While GoT experienced a huge cast explosion for season three, there aren’t expected to be nearly as many faces for season four. So far, the only major casting for the new season is Pedro Pascal (The Good Wife), who will play Prince Oberyn “The Red Viper” Martell.

EW also released the list of directors for season four, with Weiss and Benioff set for the season premiere. Alex Graves has signed on for three episodes after directing two last season. However, David Nutter, who directed season three’s ‘Red Wedding’ episode isn’t returning.

For those that have read George R. R. Martin’s books, let us know what role let us know what role you think Gatiss will have! The new season starts in 2014.

image: Wikimedia Commons/Sara Zizza