The Game of Thrones prequel has added four more cast members to its roster. According to Deadline, the HBO series House of the Dragon has recruited Rhys Ifans (Notting Hill, The Amazing Spider-Man), Steve Toussaint (Pine Gap, Shooting Dogs), Eve Best (Nurse Jackie, The King’s Speech), and Sonoya Mizuno (Devs, Crazy Rich Asians) to round out the main cast. The series, from the world of George R.R. Martin (The Winds of Winter, A Dance with Dragons), is set 300 years prior to the events of HBO’s flagship fantasy series.

According to Deadline, House of the Dragon will explore the Targaryen family lineage pulled from Martin’s novel Fire & Blood. Before there was only Emilia Clarke’s Daenerys, the world of Westeros was ruled under the Targaryen name. Ifans is set to play Otto Hightower, King Targaryen’s Hand. Described as a loyal subject to the king and his realm, he vows to protect the throne against all threats, especially those closest.

Toussaint and Best will portray Lord and wife of the House of Velaryon, according to Deadline. Toussaint as Lord Corlys Velaryon is the most famed seaman of Westeros which earns him the title of “The Sea Snake.” His wealth values higher than the Lannisters and boasts a powerful navy. His wife, Princess Rhaenys, is known as “The Queen Who Never Was” as her cousin was handed kingship simply because he was male.

This leaves Mizuno’s Mysaria, a foreigner to Westeros who worked her way to aiding royalty, Deadline reports. As a slave sold multiple times, she persevered to become the most trusted ear to the Targaryen prince, Daemon, played by Matt Smith (Doctor Who, His House). The other main cast consists of Paddy Considine (The Third Day, Hot Fuzz) as King Viserys Targaryen, Olivia Cooke (Ready Player One, Bates Motel) as Alicent Hightower, and Emma D’Arcy (Truth Seekers, Wanderlust) as Princess Rhaenyra Targaryen.

According to Deadline, Martin and co-creator Ryan Condal (Hercules, Rampage) will executive produce with Sara Lee Hess (House, Orange Is the New Black), Vince Gerardis (Game of Thrones, Flash Forward), Miguel Sapochnik (Repo Man, Bios), and Ron Schmidt (Black Snake Moan, Bessie). Condal, who wrote the pilot, will also serve as co-showrunner along with Sapochnik. The ten episode season will have direction from Spaochnik, co-executive producer Greg Yaitanes (Double Tap, Plan B), Geeta V. Patel (Meet the Patels, Project Kashmir), and Clare Kilner (How to Deal, American Virgin).

House of the Dragon is just one of the many projects HBO is planning in the expansion of the Game of Thrones universe. Talks of another prequel series have risen as well as an animated show set in the world of Westeros.