From an interview about The Witcher....the video game

http://aboutactorcharlesdance.blogspot.fr/2013/08/charles-to-voice-in-video-game.html
http://aboutactorcharlesdance.blogspot.fr/2013/09/about-charles-and-witcherthe-video-game.html

producer of the game, Mikołaj Szwed

9 – Charles Dance will be the Nilfgaardian emperor in the game. How did that come about? What traits did he bring to the game that another actor may not have been able to? Are there many Game of Thrones fans on the team?

When we were doing research on potential candidates to voice Emhyr var Emreis, Mr. Dance was always someone who came to mind. Each group of people that was consulted on the matter somehow ended up saying that we should try to reach out to him. So… we did. And he agreed to lend us his voice. As for the specific traits of his voice, what I personally like is its commanding tone. You hear a sentence and you immediately treat it as an order. This and the beautiful accent make him a splendid Emhyr! As for Game of Thrones, it’s a great show and it has a lot of fans in the studio.
http://leviathyn.com/slider/2013/09/26/witcher-3-wild-hunt-interview-charles-dance-next-gen-canon/