George RR Martin has let slip a few details about the forthcoming Game of Thrones prequel, revealing that while there may be fewer dragons in the HBO television show, there will be direwolves, mammoths and White Walkers.

The serial, which is currently being filmed in Northern Ireland, takes places thousands of years before the events in Game of Thrones and “chronicles the world’s descent from the golden age of heroes into its darkest hour”, according to HBO. Naomi Watts is lined up to star as “a charismatic socialite hiding a dark secret”, with Miranda Richardson also part of the cast. Jane Goldman and Martin himself are the show’s creators, with Goldman the showrunner.

Martin said last year that the series would show Westeros as a very different place, with no King’s Landing, no Iron Throne and no Targaryens. “Valyria has hardly begun to rise yet with its dragons and the great empire that it built,” he told Entertainment Weekly.

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On Tuesday, he revealed that the Stark family would definitely appear in the prequel, adding: “Obviously the White Walkers are here – or as they’re called in my books, the Others – and that will be an aspect of it [along with] things like direwolves and mammoths”.

The show will, however, predate the Lannisters, with another family living in the home they occupy in Game of Thrones. “The Lannisters aren’t there yet, but Casterly Rock is certainly there; it’s like the Rock of Gibraltar,” he said. “It’s actually occupied by the Casterlys — whom it’s still named after in the time of Game of Thrones.”

The novelist also revealed that the Westeros of 5,000 years ago would be split into 100 different fiefdoms. “We talk about the Seven Kingdoms of Westeros; there were Seven Kingdoms at the time of Aegon’s Conquest,” he said. “But if you go back further, then there are nine kingdoms, and 12 kingdoms, and eventually you get back to where there are 100 kingdoms – petty kingdoms – and that’s the era we’re talking about here.”

Martin is currently writing The Winds of Winter, the long-awaited sixth novel in his series A Song of Ice and Fire. In May, he promised he would have finished writing it by summer 2020, when he travels to New Zealand for a science fiction convention. “If I don’t have The Winds of Winter in hand when I arrive in New Zealand for Worldcon, you have here my formal written permission to imprison me in a small cabin on White Island, overlooking that lake of sulphuric acid, until I’m done. Just so long as the acrid fumes do not screw up my old DOS word processor, I’ll be fine,” he wrote on his website.