HBO is beginning to plot what comes after Game of Thrones when it concludes next year. The network has been working on succession plans for the show for over a year, with five potential projects in the works, and it just ordered a pilot for one of them: a prequel that takes place thousands of years before the present show, from series author George R.R. Martin and Kick-Ass and Kingsman: The Secret Service writer Jane Goldman.

“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,” reads HBO’s log line for the project.

Given the massive scale and history of the world, there’s a lot of potential for where this project could go — and the twists it could take when the truth behind these myths is revealed. The announcement does seem to rule out a couple of possibilities — at least for this project — such as a story about Robert’s Rebellion, the war fought by Ned Stark and Robert Baratheon that lead directly to the events of Game of Thrones, as well as Aegon’s Conquest, the Targaryen takeover of Westeros that took place only a few centuries beforehand.

The Hollywood Reporter says that “the project chronicles the world’s descent from the golden Age of Heroes into its darkest hour.” This seems to hint at the legend of The Night’s King, the commander of the Night’s Watch whose dark reign ended the Age of Heroes and ushered in an era called The Long Night — a story that Old Nan often used to tell young Brandon Stark. There’s also plenty of other millennia-old lore the show could potentially explore, including the construction of the The Wall, the origins of House Lannister and the Ironborn, and the first coming of Azor Ahai, the legendary hero of the Lord of Light.

But there’s a long way to go yet: Game of Thrones’ eighth season doesn’t arrive until next year, and there’s no guarantee that this pilot will lead to a series, and at the very least, we likely won’t see it for at least a year until after GOT goes off the air. THR notes that of the five projects in the works, it’s likely that not all of them will lead to a series. But it is a good sign that HBO likes this idea enough to see how it looks on camera.