HBO has begun production on 'A Knight of the Seven Kingdoms,' a 'Game of Thrones' prequel based on George R.R. Martin's novella 'The Hedge Knight,' set a century before 'Game of Thrones' and a century after 'House of the Dragon.' The series, which will have six episodes directed by Owen Harris and Sarah Adina Smith, follows the adventures of Ser Duncan the Tall (Peter Claffey) and his squire Egg (Dexter Sol Ansell). New cast members include Finn Bennett as Aerion Targaryen, Sam Spruell as Maekar Targaryen, Bertie Carvel as Baelor Targaryen, Daniel Ings as Ser Lyonel Baratheon, and Tanzyn Crawford as Tanselle. The series is expected to premiere in 2025. Additionally, George R.R. Martin announced another spin-off, 'Ten Thousand Ships,' focused on Princess Nymeria, is back in development.