Marvel had no comment on the casting.

Based on the Jack Kirby-created title, The Eternals is about superpowered and near-immortal beings known as Eternals and a more monstrous offshoot known as the Deviants that were created by cosmic beings called Celestials.

While details about the movie are being kept under wraps, sources tell The Hollywood Reporter that one aspect of the plot involves the love story between Ikaris, a man fueled by cosmic energy, and Sersi, who relishes moving amongst humans.

Zhao, an award-winning indie director behind the critical hits The Rider and Songs My Brothers Taught Me, will helm from a script by Matthew and Ryan Firpo.

Madden, who broke out on HBO's Game of Thrones playing Robb Stark, recently picked up a Golden Globe for his role in BBC's The Bodyguard. He will next be seen in Paramount's Elton John biopic Rocketman, which will debut at this year's Cannes film festival.

Madden is repped by WME, the U.K.'s Troika and Sloane Offer.