The Witcher season 2 filming is underway, but much of the casting is still being kept secret. Beyond Kristofer Hivju being cast as Nivellen, there are a number of roles that fans of the series are still waiting to learn more about. Perhaps the role that fans are most interested in seeing cast is Geralt's mentor Vesemir, and while we still don't know who will be playing the popular character in season 2, we do know who won't be.

This news comes from writer Daniel Richtman, known for his inside scoops in the entertainment industry. On February 17, Richtman tweeted about The Witcher season 2 casting Vesemir, revealing that the role has been offered to big name Hollywood stars Mads Mikkelsen and Michael Keaton. However, both Keaton and Mikkelsen apparently passed on the opportunity, though Richtman stopped short of elaborating on why.

RELATED: The Witcher Netflix Series is Still the Top Show in the World

Considering Mikkelsen's connection to video games and how many Witcher fans enjoy CD Projekt Red's video game series, it seems like he would have been a strong pick for the role of Vesemir. Mikkelsen recently portrayed Cliff in Hideo Kojima's Death Stranding in what was a critically-acclaimed and award-winning performance.

With neither Keaton nor Mikkelsen playing Vesemir in The Witcher season 2, that leaves fans to wonder exactly who will be playing the important role. It's safe to say that many would hope to see Mark Hamill as Vesemir, as the Star Wars star has even mentioned his interest in doing so on Twitter. The Witcher showrunner Lauren Schmidt Hissrich is aware of fan desire to see Hamill as Vesemir, plus Hamill has already worked on Netflix projects in the past. It seems like Hamill playing Vesemir is definitely a possibility, though whether or not it actually comes to pass remains to be seen.

Fans have also expressed interest in seeing other stars take on the role of Vesemir in The Witcher season 2. One fan even created art of Danny DeVito as Vesemir, though it's unlikely that they were serious about seeing the It's Always Sunny star as Geralt's mentor in the show.

While we don't know who will be playing Vesemir in The Witcher season 2, the casting choices so far indicate that Netflix is hoping to sign a big name talent for the role. This should help to make The Witcher season 2 an even higher profile show, though it seems fans will have to wait for more specific casting news.

The Witcher season 2 will premiere on Netflix in 2021.

MORE: Why The Witcher 3 is Still A Great Game in 2020