Game of Thrones author George R.R. Martin confirmed HBO has already axed one of five planned spinoffs based on the hit drama, which comes to an end next year.

Although Game of Thrones concluded next year with a shortened Season 8, the cable network confirmed in January that it wasn't considering just one potential spinoff series, but five. However, on the heels of the announcement that HBO has ordered a pilot from Martin and Jane Goldman set thousands of years in Westeros' past comes word that the field of possible spinoffs has already dwindled to four.

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Writing on his Not A Blog site, Martin told readers that not all of the shows will move into the pilot stage. "As for the other successor shows… if you have been following along, you know that we started with four, and eventually went to five," he wrote. "One of those has been shelved, I am given to understand, and of course Jane’s pilot is now moving to film. He also said that "three more Game of Thrones prequels," are moving forward and will be "set in different periods and featuring different characters and storylines."

Although the number of pilots has been reduced, Martin remains hopeful that at least two will make it into production. "Everything I am told indicates that we could film at least one more pilot, and maybe more than one, in the years to come," he wrote. "We do have an entire world and tens of thousands of years of history to play with, after all. But this is television, so nothing is certain."

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Set away from the War of the Five Kings that's been central to HBO's hit fantasy drama, the spinoffs won't feature existing fan-favorites like Jon Snow and Daenerys Targaryen.

News of more spinoffs to arrive in "years to come" fits HBO's timeline that the network won't start working on any Game of Thrones prequels until the main series has aired its final episodes. Martin is continuing work on the sixth novel in the series, The Winds of Winter, and confirmed his continued involvement with the television prequels won't affect his writing.