This past Summer author George R. R. Martin announced that several Game of Thrones spin-offs were in the works with HBO. The Game of Thrones TV series, based on Martin's A Song of Ice and Fire book series, will be wrapping up soon, and to prolong the property, several spin-offs have been proposed, the first being a prequel series.
Not a lot of details have been released about the new series, but HBO does have a brief synopsis of it:
Taking place thousands of years before the events of Game of Thrones, the series 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.
While that's about the extend of what we know, the first castings have been revealed. Naomi Watts (Tank Girl, King Kong, Birdman) is the first lead character cast in the prequel. No name was given for the character, but she is being described as:
"… a charismatic socialite hiding a dark secret."
The second person cast as a lead in the prequel series is Josh Whitehouse (Northern Soul, Poldark). No description of Whitehouse's character has been revealed.
The yet-to-be-titled Game of Thrones prequel is expected to start shooting in 2019.