"Game of Thrones" season 6 is welcoming a veteran actor to its astronomical cast. "The Exorcist" star Max von Sydow has been cast to play a key character, who, excitingly, fans already met during the course of the long-running HBO epic, Entertainment Weekly confirms.

Sydow was tapped to play the role of the Three-Eyed Raven, the numinous teacher to Bran Stark in the upcoming season of the award-winning series. The character already made an appearance in the season 4 finale although another actor filled in the role.

Notably, the season 4 finale was the last time Bran was seen in the series too. As previously reported by Books & Review, Bran will return to "Game of Thrones" season 6 after a season-long break. The character's last appearance saw him successfully track down the Three-Eyed Raven.

As for Sydow, EW says he won't have a lot of screen time in "Game of Thrones" season 6 even if his character is of great importance. As per Comic Book Resources, it was the Three-Eyed Raven who educated Bran of his mystical gifts and abilities, which include transferring his consciousness to animals.

The revelation on Sydow's inclusion in the series closely follows the announcement of "Deadwood" star Ian McShane also hopping on board. However, just like Jon Snow's fate, fans won't learn of the character he will play until the award-winning fantasy returns.

In a separate report by Entertainment Weekly, it was revealed that whoever the Golden Globe Award winner will portray, he won't be appearing as frequent as one would expect of a main character. Just like that of Sydow, the mystery character will only enjoy little screen time.

It's very difficult to predict who McShane is going to be in "Game of Thrones" season 6 as the new season isn't technically based on an existing book. Martin is still working on the sixth volume from the "A Song of Ice and Fire" series titled "Winds of Winter."

All five seasons of "Game of Thrones" were based on the five volumes from the book series but with the next tome still not around, the TV retelling has caught up with the books. It is still a mystery where showrunners David Benioff and Dan Weiss will take the series.

What's sure though is that HBO is open to change its previous plans just to extend it. Just recently, the network's programming president Michael Lombardo revealed to EW that Benioff and Weiss "feel like there's two more years after six."

The first 10 episodes of "Game of Thrones" season 6 will air next spring on HBO.