Executives say any spinoff will not be broadcast until after Game of Thrones'final season in 2019.
We'll bring you more on HBO'sGame of Thrones spinoff plans as we learn them.
In Game of Thrones, Valyria is gone because a mysterious event called the Doom destroyed the city, but it was in its heydey during the Age of Heroes. During the Long Night, the Children of the Forest and the First Men united with the Night's Watch to push back the Night King and the Whitewalkers to the far reaches of The Lands of Always Winter.
As for when the new Game of Thrones prequel series will begin production, that information remains unclear at this time. With a show like Game of Thrones, with the level of quality that they've set, we'd be lucky to get one that hits and we're hopeful.
"There is not going to be anything in any scenario where we have any sort of prequel air for at least a year after that", HBO programming chief Casey Bloys told Deadline in January.
The programmes logline explains: "The series chronicles the world's descent from the golden Age of Heroes into its darkest hour".
Book author George RR Martin created the new series alongside British screenwriter Jane Goldman. Goldman wrote the script and will serve as showrunner.
As for Goldman, who is expected to act as show runner on the series, her past works include X-Men: First Class, X-Men: Days of Future Past, Kick-Ass and Kingsman: The Secret Service. Goldman also wrote the screenplay for Disney's live action version of "The Little Mermaid", which is now in development.