Actors Matt Smith, Olivia Cooke, and Emma D’Arcy are the newest additions to the cast of HBO’s Game of Thrones spinoff House of the Dragon. The plot of the show is based on Martin’s Targaryen compendium Fire & Blood. Paddy Considine has already been cast as King Viserys Targaryen in House of the Dragon. Matt Smith will play the role of Prince Daemon Targaryen, King Viserys’ younger brother and heir to the throne. On the other hand Emma D’Arcy will play the role of Princess Rhaenyra Targaryen in the series.