Matt Smith will play a mad Targaryen prince in HBO’s Game of Thrones prequel

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 the prequel series, the network announced Friday.

Based on George R.R. Martin’s Fire & Blood, a history of the Targaryen family, House of the Dragon will follow the ancestors of Daenerys Targaryen, 300 years before she became one of the biggest movers and shakers in Westeros. Smith, Cooke, and D’Arcy join Paddy Considine (The Outsider), previously cast as King Viserys Targaryen.

According to HBO, this Viserys was “chosen by the lords of Westeros to succeed the Old King, Jaehaerys Targaryen, at the Great Council at Harrenhal. A warm, kind and decent man, Viserys only wishes to carry forward his grandfather’s legacy. But good men do not necessarily make for great kings.” That’s a far cry from the Viserys Targaryen of the Game of Thrones TV series, who was a rather treacherous fellow.

Smith will play Prince Daemon Targaryen, “younger brother to King Viserys and heir to the throne,” per HBO. “A peerless warrior and a dragonrider, Daemon possesses the true blood of the dragon. But it is said that whenever a Targaryen is born, the gods toss a coin in the air.” Translation: He’s not a nice guy.

D’Arcy will play Daemon’s niece, Princess Rhaenyra Targaryen, who is “the king’s first-born child.” Rhaenyra “is of pure Valyrian blood, and she is a dragonrider. Many would say that Rhaenyra was born with everything … but she was not born a man.”

Cooke is the first announced cast member who is not playing a member of the Targaryen family. Her character, Alicent Hightower, is the daughter of the Hand of the King, Otto Hightower. Alicent is “the most comely woman in the Seven Kingdoms,” according to HBO. “She was raised in the Red Keep, close to the king and his innermost circle; she possesses both a courtly grace and a keen political acumen.”

If House of the Dragon follows Fire & Blood, these three characters will become the source of — what else! — a struggle of succession involving politics, incest, and grown men seducing underage girls. The difference this time is: They all have dragons. HBO has picked up House of the Dragon with a 10-episode straight-to-series order; the network has not yet announced a release window.