By James Hibberd. July 6, 2021 8:30am. Milly Alcock and Emily Carey Courtesy of HBO. HBO’s Game of Thrones prequel has added two more cast members, and the official description of their roles Updated: The “ Game of Thrones ” prequel pilot starring Naomi Watts is not going to series at HBO, Variety has confirmed with sources. The cast and crew of the pilot were recently informed Bower had been hired to play an undisclosed role in the Game of Thrones prequel series alongside ensemble cast members Watts, Naomi Ackie, Denise Gough, Miranda Richardson, Josh Whitehouse, Sheila The prequel spinoff is set 200 years prior to the war over the Iron Throne in Martin’s “A Song of Ice and Fire” epic fantasy series, upon which HBO’s “Game of Thrones” was based. House of the Dragon, HBO’s first Game of Thrones spinoff series, is taking shape. HBO has cast Matt Smith ( Doctor Who ), Olivia Cooke ( Ready Player One ), and Emma D’Arcy ( Hanna) to star in HBO's "House of the Dragon," the first "Game of Thrones" prequel series already ordered for a full season, continues to move ahead with exciting casting news. Matt Smith ("The Crown," "Doctor Who") will play Prince Daemon Targaryen in the upcoming show, while Emma D'Arcy ("Wanderlust") will star as Princess Rhaenyra Targaryen. The upcoming series serves as a prequel to Game of Thrones, which wrapped its eight-season run in 2019. Both shows are based on the fantasy book series created by author George R.R. Martin . The nearly two-minute-long clip teases the "pursuit of legacy" that's set to unfold over the fight to claim the Iron Throne. He will join previously announced cast members Rhys Ifans, Steve Toussaint, Eve Best and Sonoya Mizuno for the Game Of Thrones prequel series from George R.R. Martin, Ryan Condal and Miguel 1bSyftL.