Controversy over the Fantastic Beasts trailer shows why J.K. Rowling should slow down the rewriting of characters.

Nagini is best known, where she is known, as Voldemort's loyal company snake in the Harry Potter universe: a magical creature that killed Snape and was finally beheaded by Neville Longbottom in his coronation of glory. But the new trailer of Fantastic Beasts: The Grindelwald Crimes, the second of the five previous films, Trigger a storm on Twitter today with the revelation that she was once a human woman. Let's try to explain why.

The trailer itself provides little context beyond another character dramatically whispering "Nagini" while actress Claudia Kim (Avengers: the era of Ultron) turns into a snake. Kim (in an interview with Weekly entertainment) and J.K. Rowling (on Twitter) throws more light on the moment of blinking of the eyes: Nagini is a maledictus, a woman who can (for the moment) pass from the human to the snake freely, but who will eventually be trapped in her serpentine form thanks to a matrilineal curse. She begins as a member of a traveling circus and friend of a struggling fugitive, Credence Barebone (Ezra Miller). How she gets from point A to Servant point of a magical fascist is still not clear.

As with Dumbledore's sexuality, Rowling says she knew Nagini's story from the beginning. But the newly-revealed background makes some aspects of the books much more troubling – including the fact that Nagini has eaten people, or the part where Voldemort lived from his "milk" (venom, we hope ) in a state of weakness. It also means that Nagini was an Asian woman who became Hitler's "pamper" for decades, which is both literally dehumanizing and an unfortunate way to bring more women of color into your story. Unfortunately, tweets like this one are no longer satirical:

The twist is the latest in a series of controversial calls for The crimes of Grindelwald, who strongly avoids recognizing that Dumbledore is gay and has proudly maintained Johnny Depp in the title role despite allegations of domestic violence. Although we have seen only a brief glimpse of the real character, Kim's Korean fans (and the Potterverse) are understandable about Nagini's apparent incarnation of the "alien foreign" trope, and for many of them, knowing that her fate – forced to support Voldemort with her bodily fluids before she was finally beheaded brutally – cast a glance at the role. The way in which the film will manage its arc remains to be seen, but the retroactive blur of lines like "You'll milk it before retiring, Wormtail" is already indisputable.