Rhys Ifans will appear as Otto Hightower, Steve Toussaint as Corlys Velaryon, Eve Best as Rhaenys Velaryon, Sonoya Mizuno as Mysaria, and Fabien Frankel as Ser Criston Cole. Five more major additions to the House of the Dragon cast have been announced.House of the Dragon Season 1 began filming on April 5, 2021.