For research, Law read several Harry Potter books that referenced Dumbledore, rather than solely watching the previous films featuring the elder character. With the help of Rowling and director David Yates, they wanted to build from the "ground up."

"I was then given the opportunity to create him without feeling the pressure to mimic or impersonate or indeed hang the character too much on past representations by the other actors," Law said.

"There were certain traits I wanted to include. I loved his humor, the twinkle he had. He sees the good in almost everyone. He has a good heart. But I was able to layer him up a little more."

Redmayne said the studio perfectly cast Law as Dumbledore, who doesn't necessarily show his true powers and appears only in about six scenes – most of which are interactions with Scamander.

"Being a formidable, formidable actor with great gravitas and weight and yet at the same time, he has this kind of playful quality," Redmayne said of Law. "And I'll never forget our first scene, which was the first time we see each other in the film. I just saw his back, basically. And the way he turned around, it was instant. It was like in one look, he had managed to inhabit that. I hadn't had any expectations about Dumbledore. But somehow it was solidified in one look."

The sequel picks up after Grindelwald was captured by the Magical Congress of the United States of America with the aid of Newt at the end of the first film. But the villainous wizard finds a way to escape custody and assembles a group of pureblood wizards who support him to rule over all humans in 1920s Paris.

Law says the film opens the door to many dramatic paths and explores a more troubled time in Dumbledore's life along with his once-close relationship with Grindelwald.

Rowling announced in 2007 that Dumbledore is gay after the release of "Harry Potter and the Deathly Hollows," the final book in the series. Some on social media criticized the author's decision to unveil and tinker with the beloved character's sexuality, but she has defended her actions.