Fantastic Beasts actress Claudia Kim breaks silence on playing Nagini

As the final trailer for The Crimes of Grindelwald just revealed, a big name from the Harry Potter books is a major part of the new Fantastic Beasts film.

Until now, Warner Bros. hasn't disclosed the name of the character played by South Korean actress Claudia Kim (Marco Polo) in the movie. Kim is none other than Nagini, a circus performer with a unique power who years later becomes Lord Voldemort's trusty killer serpent and Horcrux. Check out the video above where Kim, after keeping this secret for more than a year, is finally allowed to publicly speak her character's name for the first time.

In the new film, Nagini is a member of the traveling Circus Arcanus where she puts on a very convincing transformation act for muggles.

Kim says Nagini is far from the villain one might expect from a character who, after all, eventually kills Severus Snape. "It will be so interesting to see another side of Nagini," Kim tells EW. "You've only seen her as a Horcrux. In this, she's a wonderful and vulnerable woman who wants to live. She wants to stay a human being and I think that's a wonderful contrast to the character."

The actress reveals that when Crimes takes place in 1927, Nagini can transform from human to snake at will, yet due to her mysterious blood curse she knows that eventually, she'll become a snake permanently. "She does feel sometimes it's not controllable," Kim says. "She is bound to [permanently] transform at some point to a beast so she feels this pressure that the clock is ticking."

So, is she also a wizard then?

"She has powers that are yet to be explored," Kim says carefully. "I can't confirm she has powers like wizards have. And she doesn't have a wand."

Expect Nagini to befriend fellow a fellow outcast who has transformation issues of his own—the fugitive Credence Barebone (Ezra Miller), who has run off and joined the circus after wreaking havoc in Manhattan in the first film. "Sometimes I introduce myself as 'Credence's only friend,'" Kim says. "It's amazing these two broken souls are able to form some kind of friendship within the circus. Credence is special to her because he encourages her to use her power."

How these two will factor into the larger war against Gellert Grindelwald (Johnny Depp) remains unclear. But at least for now Kim can finally stop keeping her biggest Crimes of Grindelwald secret. "I've seen so many videos and fan theories on YouTube," she says. "Everyone is so good at analyzing every element there is. I've been very careful and aware that I should not spoil it for anybody. But I've been dying to say something!"

For more, check out the final (and best yet) Crimes of Grindelwald trailer, plus our breakdown of 20 things you missed from the new trailer; Wizarding World has a new article telling you everything you need to know about Nagini and check out our exclusive gallery of 10 new character posters.

UPDATE: Rowling explained on Twitter that Nagini's origin story has long been a part of her conception of the Harry Potter universe:

Fantastic Beasts: The Crimes of Grindelwald opens Nov. 16.