Albus Dumbledore’s relationship with Gellert Grindelwald is key to understanding a crucial time in wizarding history — something that Fantastic Beasts: Crimes of Grindelwald will explore.

That’s why Warner Bros. and director David Yates upset Harry Potter fans earlier this year when they announced Crimes of Grindelwald won’t address Dumbledore’s sexuality. Dumbledore wasn’t just good childhood friends with Grindelwald; author J.K. Rowling said Dumbledore was madly in love with the dark wizard. Dumbledore’s adoration for Grindelwald, Rowling said in 2007, played a key part in a catastrophic turn of events for both friends and the wizarding world-at-large.

“Falling in love can blind us to an extent,” Rowling said at the time. She went on to describe the love Dumbledore had for Grindelwald as a “great tragedy.”

Crimes of Grindelwald will explore Grindelwald’s transformation into a dark wizard, and Dumbledore’s painful quest to try and stop him from achieving his very Ur-Fascistic philosophical goals. Their relationship is integral to the film’s storyline. New footage from San Diego Comic-Con, and input from the cast provides a little more clarity over how Yates will handle that relationship.

The Mirror of Erised appears halfway through the new Fantastic Beasts trailer. Harry Potter fans will instantly recognize the mirror that captivates Harry in Harry Potter and the Philosopher’s Stone. In this movie, his nightly strolls down to the abandoned mirror turn into fantastical wish fulfillment’s as the mirror shows him a world in which his parents are still alive. That’s what the Mirror of Erised does — it casts an image of what the person standing before it truly desires.

Dumbledore, standing in front of the Mirror in the Fantastic Beasts trailer, sees Grindelwald. His relationship to both Grindelwald, and the Mirror, is a big part of Harry Potter lore. Rowling penned a blog post for Pottermore, a website dedicated to everything Harry Potter, that “Professor Dumbledore makes key modifications to the mirror (which has been languishing in the Room of Requirement for a century or so before he brings it out and puts it to work).” Dumbledore specifically dug the mirror back out in Harry’s first year as an effort to hide the Philosopher’s Stone, created by Nicolas Flamel, from Voldemort. The insinuation, however, is that he’s used it in the past, alongside other Hogwarts professors.

The only real glimpse Rowling ever gives us into Dumbledore’s thoughts on the Mirror and its wicked capabilities comes through a conversation with Potter in The Philosopher’s Stone.

“It shows us nothing more or less than the deepest, most desperate desire of our hearts,” Dumbledore told Potter. “It does not do to dwell on dreams and forget to live, remember that.”

Rowling added a few more notes on the mirror in that same Pottermore blog post, writing, “Dumbledore knows that life can pass you by while you are clinging on to a wish that can never be — or ought never to be — fulfilled.

“The mirror is bewitching and tantalizing, but it does not necessarily bring happiness,” she wrote.

Dumbledore seeing Grindelwald, the object of his desire, signified the importance of their relationship. This is especially true as Dumbledore fought against against Grindelwald’s group of pre-Death Eater supremacists who viewed Muggles (non-magical people) as less than wizards and witches.

The scene acts as proof that Grindelwald is Dumbeldore’s deepest desire, but that doesn’t explicitly address the two’s relationship. Jude Law, the actor who plays Dumbledore, told Entertainment Weekly after the trailer debuted that Grindelwald acts as a kind of temptation for Dumbledore.

“It’s no secret that there was an incredibly intense relationship shared by these two in the past,” Law said. “[Grindelwald] sits very much at the center of Dumbledore’ … his desires, but also the darkest parts of himself. And in a way, I think that’s what Grindelwald perhaps symbolizes for everyone: He’s temptation. He kind of empowers you but he also, I suppose, opens up the worst parts of you.”

Law’s statements hint at a romantic history between the two, but his caveat about “powerful beings” acting as temptation does lead to more questions about what that relationship will look like on screen. Laws’ words to echo what Yates said in February, who also spoke to Entertainment Weekly about the relationship.

“He had a very intense relationship with Grindelwald when they were young men,” Yates said. “They fell in love with each other’s ideas, and ideology and each other.”

Fans will have to wait and see how the relationship between Dumbledore and Grindelwald plays out. Fantastic Beasts: Crimes of Grindelwald will be released on Nov. 22.