One of the things I like best about Fantastic Beasts and Where to Find Them is that it’s not a Harry Potter re-tread. It’s legitimately building off the world J.K. Rowling established with her novels and then taking it in a new direction. It’s not another coming-of-age story and it’s not a re-introduction to the magical world. While you don’t need to have seen or read Harry Potter to appreciate Fantastic Beasts, you’ll definitely be ahead of the curve if you’re a fan of the books.

I mention the books specifically because the good folks over at ScreenCrush spoke with a Harry Potter expert Jackson Bird, Director of Wizard-Muggle Relations (that’s his real title, and it’s better than any title I will ever hold) from the non-profit organization the Harry Potter Alliance. Bird knows the books backwards and forwards and he picked up on a surprising connection between Fantastic Beasts and Harry Potter and the Deathly Hallows.

[Spoilers ahead if you haven’t seen Fantastic Beasts and read Deathly Hallows]

In Fantastic Beasts, the major threat that Newt Scamander has to face is an “obscurus”. It’s described as “an unstable, uncontrollable dark force that bursts out and attacks,” and it’s the result of a magical person trying to suppress their magic. Obscura usually kill their host before they reach the age of ten, and they only grow more powerful the older the host is. In the case of Credence, who’s a teenager, his obscurus is able to ravage New York City.

So what’s the connection to Deathly Hallows? Here’s a quote from the book where Aberforth Dumbledore, Albus’ brother, explains what happened to their sister, Ariana:

“It destroyed her what they did, she was never right again. She wouldn’t use magic, but she couldn’t get rid of it. It turned inward and drove her mad, it exploded out of her when she couldn’t control it and at times she was strange and dangerous.”

That sounds a lot like an obscurus, and if that’s the case, then it’s possible that’s where Grindelwald first learned about the creature due to his relationship with Dumbledore. So the connection is that Grindelwald learned about the obscurus when he encountered Ariana Dumbledore, and that’s why he knows so much about it when he’s investigating it under the guise of Percival Graves while he’s in America.

Also, if you think the obscurus is something Rowling just made up for the movie, think again. The name of the imprint on the book Fantastic Beasts and Where to Find Them is “Obscurus Books”.

Check out the video from ScreenCrush below.