Bloodmoon was the production title of HBO's first Game of Thrones spin-off series. It was colloquially referred to as Game of Thrones: The Long Night. It was to be set during the Age of Heroes, millennia before the original TV series, and was intended to depict the events of the Long Night. It was one of multiple Game of Thrones prequel projects being actively considered for development by HBO.
On October 29, 2019, it was confirmed that the spin-off had been officially canceled.
On June 8, 2018, HBO put out a press release that it had ordered a pilot episode for the prequel pitch by Jane Goldman - with George R.R. Martin attached as a co-producer. It provided this short description for the prequel:
"Taking place thousands of years before the events of Game of Thrones, the series chronicles the world's descent from the golden Age of Heroes into its darkest hour. And only one thing is for sure: from the horrifying secrets of Westeros's 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."
Martin stated in an interview with The New York Times from November 2018:
"It's set thousands of years before Game of Thrones. King's Landing does not exist. The Iron Throne does not exist. There are no dragons there."
George R.R. Martin unofficially referred to the show as The Long Night, although the title Bloodmoon was used instead as a production title. On November 5, 2018, Martin said:
"HBO has informed me that the Jane Goldman pilot is not (yet) titled THE LONG NIGHT. That is certainly the title I prefer, but for the moment the pilot is still officially UNTITLED. So...mea culpa, mea culpa, mea culpa. Elsewise, the pilot is coming along well, with casting falling into place."
Jane Goldman was announced as head writer and showrunner. It is also known that, in contrast with Game of Thrones, this series will have a full "writing staff"; as Benioff, Weiss, and Cogman were the only writers for most of the series, aside from a few guest writers earlier on.
George R.R. Martin's actual level of involvement in creating and writing Bloodmoon is largely tangential, and only in an advisory role. In an interview with The New York Times on November 30, 2018, Martin explained that he didn't have unpublished notes on the Long Night, nor plans to develop any narrative in it.
In his interview with The New York Times, Martin stressed that the Long Night prequel was "mostly" the creation of Jane Goldman. In his own words:
"If you look at the published books so far, there's really very little material about [the Age of Heroes and the Long Night] — a sentence here, a sentence there. Old Nan tells a tale that takes up a paragraph. So Jane had to create the characters, the settings and some of the events, and we had to look at everything that was said and say, 'O.K., here’s what was said at this point, we need to make it consistent to that.' We kicked around some ideas and I made some suggestions. But mostly it's been Jane running with it."
- Naomi Watts as "a charismatic socialite hiding a dark secret."
- Josh Whitehouse as Unknown
- Georgie Henley as Unknown
- Naomi Ackie as Unknown
- Sheila Atim as Unknown
- Ivanno Jeremiah as Unknown
- Jamie Campbell Bower as Unknown
- Denise Gough as Unknown
- Alex Sharp as Unknown
- Toby Regbo as Unknown
- HBO, "What to Know About the Game of Thrones Prequel" (Archived)
- The Hollywood Reporter, "'Game of Thrones': Naomi Watts-Led Prequel Dead at HBO"
- Entertainment Weekly, "Game of Thrones prequel pilot ordered by HBO: All the details..."
- The New York Times, "George R.R. Martin on How 'Nightflyers' Made 'Game of Thrones' Possible"
- Not A Blog: "Football, Fire, and Other Stuff"
- Variety, "'Game of Thrones' Prequel Casts Naomi Watts in Lead Role"
- Deadline, "Josh Whitehouse Set As 'Game of Thrones' Prequel Lead"
- Entertainment Weekly, "Game of Thrones prequel announces diverse full cast, female director"