The British musician will play a character of a drummer which is similar to his real life profession, reported Ace Showbiz.
"Game of Thrones" season 3 has been filmed since July for a March 31, 2013 premiere on HBO. It's filmed in several locations, which are Northern Ireland, Croatia, Iceland and Morocco.
The new chapter will feature a bunch of new characters, including Mance Rayder (Ciaran Hinds), Jojen Reed (Thomas Sangster), Meera Reed (Ellie Kendrick) and many more.
"If you hurl 300 characters at an audience, the story collapses under the weight of too many faces, too many names, and too many subplots.
"We need to be just as mindful of the audience members who have never read the books as we are of the readers; the series will fail if we only appeal to those who already know the characters. So we try to be parsimonious about how many new roles we introduce to the story and when we introduce them," said showrunner David Benioff.