The new of 58-year-old British actor's entry in the show broke after the HBO drama series was added as his most recent television work by his talent agency.
Details about his role are still under wraps.
The fantasy drama recently cast Freddie Stroma as Samwell Tarly's younger brother Dickon, roped in Pilou Asbaek to play Theon's uncle Euron Greyjoy, and replaced Struan Rodger with Max von Sydow as the Three-Eyed Raven.
Ian McShane will also be a part of the new season that will air in 2016.