Jane Goldman will serve as showrunner on the new series, set thousands of years before the events of 'Thrones' and co-created by source-material author George R.R. Martin.

The future of the Game of Thrones franchise has become clearer, and that future lies firmly in the past.

HBO is officially moving forward with a pilot order for a still-untitled Game of Thrones prequel, created by Jane Goldman (Kick-Ass, Kingsman: The Secret Service) and George R.R. Martin — the author of the A Song of Ice and Fire novel series on which Thrones is based.

Set thousands of years before the events of Thrones, the project chronicles the world's descent from the golden Age of Heroes into its darkest hour. A logline from the network teased the plot without divulging any specifics: "Only one thing is for sure: From the horrifying secrets of Westeros' history to the true origin of the White Walkers, the mysteries of the East to the Starks of legend — it's not the story we think we know."

The pilot is based on a story from Goldman and Martin, with the teleplay credited to Goldman. Goldman will also serve as showrunner. In addition to Goldman and Martin, executive producers on the series include current Game of Thrones producer Vince Gerardis, as well as Damages and Bloodline co-creator Daniel Zelman.

Goldman and Martin's Game of Thrones prequel is the first of several potential series set in the world of Westeros to move forward at HBO beyond the script phase. In May 2017, a multitude of writers were revealed by HBO to be working on what Martin himself has described as "successor shows." Those writers include Goldman, Max Borenstein (Kong: Skull Island), Brian Helgeland (Legend), Carly Wray (Westworld) and Thrones veteran Bryan Cogman. Game of Thrones creators and showrunners David Benioff and Dan Weiss are uninvolved in the successor show effort, focusing instead on the forthcoming final season of Thrones after more than a decade spent wandering the world of the Seven Kingdoms.

Speaking previously with The Hollywood Reporter, HBO's Casey Bloys said that any Game of Thrones successors, if greenlighted, would not air "until at least a year after the final season." Bloys also added that he did not expect every one of the scripts to move forward beyond the page.

"I think that is probably unlikely," Bloys told THR in July 2017. "This show is very special. I'm not looking to have as many as possible. My sense right now is, we would be very lucky if one of the four rises to the level that we have set. Now, theoretically, what if they're all great? That's a high-class problem that I'll solve when it comes to that. But knowing what we know about the development process, that's why we wanted to increase our odds. But I do not see a scenario where we have more than one. But again, high-class problem."

"I'll do anywhere from zero to five," he added in a January 2018 interview. "Though probably more likely one. But we'll see."

Follow THR.com/GameOfThrones for more news about Goldman and Martin's Game of Thrones prequel.