Game of Thrones author George R.R. Martin has confirmed that the first of up to five potential prequel shows will be called The Long Night. The HBO show is expected to begin filming in early 2019, ready to take up the mantle after Game of Thrones' final season, and just cast Naomi Watts in a mystery role as a "charismatic socialite hiding a dark secret."
It's unclear how many of the five prequel shows in development will actually make it to the screen, but Martin has previously said that their settings range from 100 years prior to the events of Game of Thrones, to 5000 years. "The Long Night" refers to Westeros' own personal Dark Age - a period of time thousands of years before Robert's Rebellion, when the world experienced a winter that lasted for many years and brought with it the White Walkers and their army of wights.
Commenting on Watts' casting in a blog post, Martin opened with the statement, "Casting is now underway for THE LONG NIGHT, the first of the GAME OF THRONES successor series to ordered to film" - thereby confirming the rumored title for the show. He also teased that writer Jane Goldman and the rest of the Long Night team are currently "neck deep in casting," so there will likely be more names announced soon. Intriguingly, he also indicated that readers can find details related to one or more of the prequel shows in his upcoming book, Fire & Blood.
Fire & Blood is, Martin has said emphatically, not a novel but an "imaginary history" of Westeros that spans almost a thousand manuscript pages and will include plenty of illustrations. Fire & Blood is the first in a series of such books, and will focus specifically on the line of Targaryen kings from Aegon I to Aegon III. In his blog post, Martin wrote:
"There are still a couple of other possible prequels in active development. I can’t tell you the subject matter of those projects, no, sorry, wish I could. The readers among you might want to grab a copy of FIRE & BLOOD when it is released on November 20, though."
That seems like a pretty clear indication that, as many have suspected, one of the prequel ideas was for a show focused on earlier members of the Targaryen lineage. As for The Long Night - well, the title suggests that the show might take place during that dark time, though it's hard to imagine how a "charismatic socialite" like Watts' character might fit into that setting. Hopefully as more casting news breaks, we'll get a clearer indication of what to expect.
Source: George R.R. Martin