After lengthy negotiations, Naomi Watts has signed on to lead the ensemble cast of HBO’s Game Of Thrones prequel pilot, from writer Jane Goldman and author/GOT co-executive producer George R.R. Martin.

Created by Goldman and Martin and written by Goldman based on a story by her and Martin, the untitled prequel takes place thousands of years before the events of Game Of Thrones. It 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’ 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.

The creative team behind the project is not giving away much about Watts’ character — she will play a charismatic socialite hiding a dark secret.

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Goldman serves as showrunner and will executive produce alongside Martin as well as fellow GOT co-executive producer Vince Gerardis and Damages and Bloodline co-creator Daniel Zelman. Added since the June pilot green light are former BBC Studios executive James Farrell and Jim Danger Gray (Orange Is the New Black, Hannibal) as executive producers and Chris Symes (The Alienist) as co-executive producer. As previously announced, GOT creators/exec producers David Benioff and D. B. Weiss have no involvement in the potential offshoots.

GOT, created by Benioff and Weiss, has a male lead, Jon Snow. Looking to differentiate itself from the mothership series and coming from a female writer, Goldman, it was a logical assumption that the prequel could have a female lead, something Watts’ high-profile casting seems to reaffirm. That is not exactly the case, HBO President of programming Casey Bloys told Deadline in July.

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“There are very strong female characters but it’s an ensemble, there are men and women,” he said. “Jane is a very good writer, we don’t want to limit her to writing female leads. There are a lot of very complicated leads in (the pilot).”

None of the actors from the current show will appear on the prequel, which originally was set 8,000 years before GOT. “It’s a very different setting, a very different time in Westeros, It will feel different but still Game of Thrones,” Bloys said in August.

Two-time Oscar nominee Watts recently signed on to star as Gretchen Carlson opposite Russell Crowe in Showtime’s Roger Ailes limited series. She most recently starred in Ophelia with Daisy Ridley and will next be seen in Once Upon a Time in Staten Island, The Wolf Hour, Boss Level and Luce. Other recent projects include David Lynch’s Twin Peaks sequel limited series for Showtime, Netflix’s Gypsy series, Colin Trevorrow’s The Book of Henry, and The Glass Castle with Brie Larson and Woody Harrelson. Watts is repped by CAA; Untitled Entertainment and Hansen Jacobson Teller.