News of the Game of Thrones spinoff has been largely speculative, but today we learned some bombshell casting info that until now had only been rumor — Hollywood darling Naomi Watts has signed on for a leading role!

According to Deadline, Watts — an accomplished actress whose credits include Mulholland Drive, The Ring, King Kong, Eastern Promises, Birdman or (The Unexpected Virtue of Ignorance), St. Vincent and The Divergent Series — has been secured “to lead an ensemble cast” for the spinoff, which is reported to be a prequel that tells the story of the Age of Heroes and the Long Night, events that happened thousands of years before those taking place in both the Song of Ice and Fire series and the Game of Thrones TV show. The working title of the prequel is, unsurprisingly, The Long Night.

Naturally, HBO is not saying much about Watts’ character, but Deadline is reporting that “she will play a charismatic socialite hiding a dark secret.” They also note that, given that the writer of the prequel is Jane Goldman and that the show is looking to “differentiate itself” from its namesake series, “it was a logical assumption that the prequel could have a female lead.” This isn’t being confirmed by anyone at HBO — and in fact, in July HBO president of programming Casey Bloys told Deadline that they didn’t want to “limit” Goldman to writing mostly female characters — but given this news, it’s certainly tempting to believe that The Long Night will feature a female lead.

Deadline also notes that the casting was confirmed after “lengthy negotiations,” which, for an actress of Watts’ caliber, makes sense. In fact, here at Watchers we’d heard strong rumors of this casting during the negotiations, but it’s nice to have it confirmed at last.

What does this casting news mean for the spinoff? And who could Watts be portraying? Let us know your thoughts in the comments below!