According to Redanian Intelligence, the new spinoff is currently in development and will chronicle the adventure of a group of young Nilfgardians known as The Rats.
Similar to CD Projekt RED's games, Netflix’s The Witcher is based on a series of books of the same name by Polish author Andrej Sapkowski. According to the books, The Rats are a group of misfits that take Ciri in after she is separated from Geralt in the books.
The group had six members: Giselher, Mistle, Reef, Iskra, Kayleigh, and Reef before they admitted Ciri into their ranks. They will be introduced in the series for the first time in episodes 7 and 8 of the upcoming third season, which will premiere next summer, before getting even more screen time in the fourth season. The spinoff series will drop somewhere between season 3 and season 4 of The Witcher.
At the moment, there's no info on the release date, plot, or title of the show. But, it's safe to assume that members of the gang are slated to appear in the third and fourth seasons of The Witcher will reprise their roles in the series. Christelle Elwin, of Netflix’s Half Bad and Bloods fame, will star as Mistle, while Fabian McCallum, from Amazon’s The Lord of The Rings: Rings of Power and Time of Contempt, will star as Kayleigh. Also, Juliette Alexandra will play Reef and there is a high probability that Aggy K. Adams will portray Iskra. Finally, Andrew Lee Potts, Ben Radcliffe, and Ash Rizi will also star in the upcoming third season although their roles are currently unknown.
It is currently unknown what part of the gang’s existence the spinoff will explore, whether it is before they meet Ciri or during their time together. Nevertheless, as time passes, we'll see more details come to light and fans will learn more about the planned spinoff series.
The still-untitled spinoff will be Netflix’s second from the world of The Witcher. The first spinoff, titled Blood Origin, is a four-episode limited series dropping on the streaming platform on Christmas Day. A few weeks ago, Netflix dropped a teaser trailer for the series, which has since racked up over two million views, demonstrating fan interest.
By the way, Netflix’s recent announcement that Liam Hemsworth will replace Henry Cavill as the titular character from the fourth season of The Witcher generated a lot of angst on the internet. Fan reactions to the announcement were largely negative with some going as far as to threaten a boycott of the entire series.