• Netflix presents Marvel's Iron Fist at New York Comic-Con 2016.

Netflix presents Marvel's Iron Fist at New York Comic-Con 2016. (Photo : Craig Barritt/Getty Images for Netflix)

A major casting development for Netflix's "The Defenders" has just been revealed. The Marvel TV series has just signed Sci-Fi Movie Queen Sigourney Weaver for a mysterious role, sources confirm.

Confirmation of Weaver's role in "The Defenders" came as a big surprise to everyone in New York Comic Con. As a matter of fact, the Golden Globe winner will portray the show's main villain, which means she's going against the superhero quartet consisting of Luke Cage, Daredevil, Jessica Jones and Iron Fist.

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At the "The Defenders" panel, Marvel TV executive Jeph Loeb warned the audience not to leave early, otherwise they'll miss something big. He then introduced unannounced panel guests Charlie Cox ("Daredevil"), Krysten Ritter ("Jessica Jones"), Mike Colter ("Luke Cage") and Finn Jones ("Iron Fist"). Weaver then came out to join the rest of the panel on stage.

"Marvel is honored to have an actress of her caliber and status join what is already our biggest show ever! She is by definition a class act," TVLine quoted Loeb as saying.

Although nothing else was revealed about Weaver's big bad character, there are already some theories as to which role she might portray.

IGN lists Viper as one of the potential villains Weaver might play. The character has ties to The Hand, a recurring character in "Daredevil" and a prominent figure in "Iron Fist." She was previously the head of Hydra, which is the main nemesis of the Avengers in the Marvel Cinematic Universe.

Another possibility is The Beast, a demon that makes use of the Hand in order to pursue its desire for destruction. It can possess anyone's body, so it's possible Weaver's character is just a host for The Beast.

With Luke Cage now available on Netflix, the next Marvel series to debut is "Iron Fist." As per the preview presented at NYCC, "Iron Fist" will be more martial arts-heavy compared to "Daredevil."

At the panel, the cast of "Iron Fist" discussed the intense secrecy surrounding Marvel's TV and movie projects, sharing that the cast didn't get their scripts until they were just about to begin filming.

"Iron Fist" is slated to premiere on March 17, 2017.