The Game of Thrones prequel is now in the works, and HBO has revealed its all-star cast. There are a lot of speculations about what the new series will be like, but the network confirmed it is set in the time of the Age of Heroes when the White Walkers first step in Westeros.

The fan site Watchers on the Wall revealed the Game of Thrones prequel is now in production at Glenariff, a valley in Northern Ireland. It is the same place where the Vale of Arryn was set, where Sansa (Sophie Turner) and Littlefinger (Aidan Gillen) went after the Purple Wedding. Filming also happens in Belfast, where the original show was also filmed.

There are speculations the prequel will be titled Bloodmoon. But just like other television and movie projects that use codenames, it is possible it is not its actual title. According to Newsweek, George R.R. Martin prefers to call the new series The Long Night, which refers to Game of Thrones Season 8 Episode 3's battle of Winterfell.

HBO has revealed the all-star cast that would lead the Game of Thrones prequel, starting with Naomi Watts. Although the network has yet to confirm her role, the two-time Oscar-nominated actress is said to play a "charismatic socialite hiding a dark secret." The Telegraph reported the 50-year-old star's character description is quite similar to Cersei (Lena Headey), so it might be safe to assume that she could be a Lannister ancestor.  

However, there are also theories Watts will play the role of Nissa Nissa, a prominent figure in the Westerosi lore. Nissa Nissa is the wife of the ancient hero, Azor Ahai, who is also known as the Lord of Light and the epitome of the R'hllor faith. He is said to be the one who forged the magical sword, Lightbringer, by plunging it through the heart of the one he loves so he could defeat the White Walkers.

Josh Whitehouse will also join the Game of Thrones prequel. The Poldark star will reportedly play a major role, although it has yet to be revealed. The Harry Potter Miranda Richardson, who is best known for her role as Rita Skeeter, will also be in the new HBO series.

Other stars that will be in the Game of Thrones prequel are the rising stars like Naomi Ackie, Jamie Campbell Bower, Ivanno Jeremiah, Toby Regbo, and Georgie Henley. There will also be theatrical actors like Denise Gough, Sheila Atim, John Simm, Marquis Rodriguez, Richard McCabe, John Heffernan, Dixie Egerickx, and Alex Sharp. The new series may hit the small screens in 2021.