'Game of Thrones' Season 6 SPOILERS: Richard E. Grant Joins Cast in Mystery Role

The cast of HBO's Game of Thrones continues to grow for Season 6, and some new spoilers indicate that yet another actor, Richard E. Grant, has joined the cast in a mystery role.

Watchers on the Wall, which cites the agency CV of the British actor, reports that Grant's most recent television credit is Game of Thrones. No role or episode director is listed, nor has HBO made an official casting announcement of any kind.

Grant is a storied television and film actor who recently appeared in the television series Dig and has also shown up on Downton Abbey, Doctor Who, and fellow HBO show Girls. He first gained notoriety in Withnail & I, and has acted in a wide assortment of television and movies since then, including Henry and June, L.A. Story, Bram Stoker’s Dracula, Spice World, Gosford Park, and The Iron Lady.

But who is Grant playing in Season 6? There are numerous possibilities, as Game of Thrones has many unfilled roles for this upcoming season, including Randyll Tarly, Aeron Greyjoy, Lord Karstark, and Smalljon Umber, just to name a few. If the show takes some liberty with the character descriptions, then Grant could potentially play any of the characters, with the exception of Smalljon Umber and the new Dothraki characters.

Grant joins a growing list of new additions for Season 6. Freddie Stroma was recently cast as Samwell Tarly's brother. Entertainment Weekly reported that the HBO series had brought in the UnREAL star as Dickon Tarly, the brother of the fan-favorite member of the Night's Watch and best friend of the deceased Jon Snow (Kit Harington).

Acclaimed actor Ian McShane has joined the show also in a mystery role, and Max von Sydow, who has starred in numerous films, has agreed to play the Three-Eyed Raven, the magical mentor of Bran Stark. We last saw this character in the Season 4 finale, though he was played by a different actor.

What do you think of Grant's casting? Who do you think heis playing in Season 6 of Game of Thrones? Let us know in the comments section below.