Development continues on HBO's plans to expand on the world of Game of Thrones, the upcoming House of the Dragon. According to EW the series has entered a crucial stage of the early works and has begun casting. At this point it's unclear which characters from George R.R. Martin's world will even appear in the series with the outlet noting that "just because characters are in Martin's book doesn't necessarily mean they will be in the series or be the same as their book descriptions." The series will focus on the Targaryen family though so expect some fresh faces with that Daenerys-like hair.
EW also notes that the series will, at some point, tackle the titular "Dance of Dragons" from Martin's books. This Targaryen civil war was fully examined in Martin's Fire & Blood, which traced the entire lineage of the Targaryen family from the creation of the Iron Throne up through this civil war. It seems likely that these events will be dramatized in the series.
Behind the scenes on House of the Dragon HBO has assembled a team of franchise alums to make the series work. Miguel Sapochnik, who helmed the Thrones episodes "Battle of the Bastards" and "The Long Night," will direct the pilot and additional episodes. Colony showrunner Ryan Condal and Sapochnik will partner as showrunners on the series, which will be written by Condal.
“The Game of Thrones universe is so rich with stories,” Casey Bloys, president, HBO programming, said in a statement when the series was ordered. “We look forward to exploring the origins of House Targaryen and the earlier days of Westeros along with Miguel, Ryan and George.”
Martin himself previously promised that, while he is excited for the new prequel, he won't let that project deter him from completing the last two books in his A Song of Ice and Fire series.
"I expect to be involved in [the production of House of the Dragon] to some extent… and, who knows, if things work out, I may even be able to script a few episodes, as I did for the first four seasons of Game of Thrones," Martin shared on his blog. "But… let me make this perfectly clear… I am not taking on any scripts until I have finished and delivered Winds of Winter. Winter is still coming, and Winds remains my priority, as much as I’d love to write an [episode] of House."
HBO's Bloys previously made his "best guess" for when the series would debut sometime in 2022, a comment made prior to the coronavirus outbreak.