In an interview with Entertainment Weekly, creator George R.R Martin stated that this prequel is set roughly 5,000 years before the events of Game of Thrones. "We are dealing with a different and older world," Martin told EW. In the interview George R.R Martin also said "Westeros is a very different place." King's Landing won't even exist yet, and as a result, there's no Iron Throne, either. Meanwhile, Valyria will have "hardly begun to rise," Martin explained. "it's not the story we think we know." It will teach us more about Westeros history, the white walkers origins, and "the mysteries of the East."
George R. R. Martin expressed his preferred title for this series was "The Long Night."
Began filming on 13 May 2019 in Belfast under the working title "Bloodmoon."
The pilot takes place five thousand years before the events of Game of Thrones, before the Targaryen dynasty and the Iron Throne existed, during the so called "Long Night."
HBO announced on 29 October 2019 the pilot would not be turned into a series. After viewing the pilot, HBO was reportedly "not thrilled by the results" and even gave showrunner Jane Goldman and her team notes on changes needed, but even after the re-edit of the pilot, HBO was still "not thrilled" and decided not to green light the pilot to series. Hours after the cancellation, HBO green lighted instead another 'Game of Thrones' prequel co-created by George R.R. Martin and Ryan Condal, based on the Targaryen dynasty, which became House of the Dragon (2022).