She played a major role in the Harry Potter series as Lord Voldemort's minion and anchor to life. He turned her into a horcrux after killing Bertha Jorkins in Albania, shortly before the events of Goblet of Fire.
However, The Crimes of Grindelwald will explain that Nagini was once a cursed human (played by Claudia Kim), who traveled with a magical circus (the Circus Arcanus, to be exact), enthralling crowds with her ability to transform into a serpent.
“It will be so interesting to see another side of Nagini,” Kim told Entertainment Weekly. “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.”
Unfortunately for Nagini, she is destined to eventually lose the ability to transform at will. The cursed affliction turns a person into what is known as a Maledictus, but does not necessarily put them on the same level as wizards/witches and Animagi.
“She has powers that are yet to be explored,” Kim added. “I can’t confirm she has powers like wizards have. And she doesn’t have a wand.”
Here's her character poster for the sequel:
While with the circus, Nagini finds a kindred spirit in the form of Credence Barebone (Ezra Miller), a wizard who repressed his powers for so long, that he became an Obscurus. After causing a ton of damage and mayhem in Manhattan, he decided to perform on the road as well.
“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," Kim said.
Does her scaly fate turn Nagini into a bitter, black-hearted soul that makes her more susceptible to Voldemort's evil persuasions and his plans for pure-blooded wizarding world domination? Probably.
Fantastic Beasts: The Crimes of Grindelwald slithers into theaters Nov. 16.