Ryan Condal (Hercules) penned this script, which will be executive produced by GoT author George R. R. Martin and based on his latest book release, Fire & Blood, a hardback novel detailing the history of House Targaryen covering roughly 150 years.
The first Game of Thrones prequel has just recently wrapped filming and will star Naomi Watts, who plays a personable socialite (apparently, they have those in Westeros, too) with a dark secret. Miranda Richardson (the Harry Potter films), John Heffernan (Dracula), John Simm (Strangers), Marquis Rodriguez (Manifest) and Richard McCabe (Philip K. Dick’s Electric Dreams) will also star. Additionally, Dixie Egerickx (Summerland), Josh Whitehouse (Poldark), Naomi Ackie (Lady Macbeth), Denise Gough (Monday), Sheila Atim (Harlots), Ivanno Jeremiah (Humans) and Jamie Campbell Bower (the Fantastic Beasts films), Georgie Henley (The Chronicles of Narnia films), Alex Sharp (How to Talk to Girls at Parties) and Toby Regbo (Fantastic Beasts: The Crimes of Grindelwald) are slated to appear.
The first sequel, rumored to be called Game of Thrones: The Longest Night, was written by Jane Goldman (X-Men series). This prequel will predate the Targaryen one (rumored to be called Fire & Blood because of the history book it's based on) by thousands of years, and is rumored to take place before the the Long Night and reveals the terrifying secrets of Westeros’s history. GRRM revealed that it touches on the genesis of the White Walkers, the great mystery of the East and the legend of the first Starks, whereas the Targaryen Civil War, the Dance of Dragons, took place about 200 years before the events of the Game of Thrones series we know and love.
While a premiere date for the first prequel starring Watts is still pending, we're betting we'll see The Longest Night next year, and Fire & Blood by 2021.