On Tuesday, HBO picked up House of the Dragon, which is set 300 years before the events of Game of Thrones. The series is co-created by author George R.R. Martin, whose fantasy novel series, A Song of Ice and Fire, was adapted into the HBO hit show.

HBO programming president Casey Bloys made the announcement during the WarnerMedia investor day, as the company unveiled new details about the upcoming HBO Max streaming service.

House of the Dragon is based on Martin’s book, Fire & Blood, and tells the story of House Targaryen, which once ruled the Seven Kingdoms of Westeros.

Ryan Condal, who co-created the series with Martin, will serve as showrunner alongside Miguel Sapochnik, who will direct the pilot and additional episodes.

“The Game of Thrones universe is so rich with stories,” said Bloys in a statement. “We look forward to exploring the origins of House Targaryen and the earlier days of Westeros along with Miguel, Ryan and George.”

There was no initial word on when the prequel would go into production or debut on HBO.

The news came the same day that HBO passed on another Game of Thrones prequel, which took places thousands of years before Thrones and had starred Naomi Watts. HBO had shot a pilot for the Watts-led prequel but decided not to move forward with it.

HBO has been moving aggressively to continue the Game of Thrones franchise, developing five separate spinoff projects to its most-watched series ever (45.9 million viewers tuned into the drama’s eight and final season this past spring).

Last week, Adweek named Game of Thrones its Show of the Year as part of the annual TV Hot List.

More than 100 brands collaborated with HBO and Game of Thrones during the show’s final season, including AT&T, Mountain Dew, Urban Decay and, most memorably, Bud Light, in a Super Bowl spot that featured one of the show’s dragons incinerating the Bud Knight. Last month’s Emmys served as the final curtain call for the show, which won 12 awards, including outstanding drama series.