Harry Potter creator JK Rowling says she is "delighted" Johnny Depp has a role in Fantastic Beasts and Where to Find Them and its planned sequels.
The British author said Depp had done "incredible things" with the character of dark wizard Grindelwald.
Depp makes a fleeting appearance in the first Fantastic Beasts film but will play a larger part in its sequel .
Director David Yates said Depp was an "extraordinary talent" as well as "a huge Potter fan".
"He was beyond excited about working on this material," said Yates at the world premiere of Fantastic Beasts in New York.
The film, a prequel to Rowling's wizarding series, is set 70 years before the events depicted in the first Potter book.
In those stories, Grindelwald was a good friend of Albus Dumbledore, future headmaster at the Hogwarts School of Witchcraft and Wizardry.
But their close relationship eventually broke down - a plot thread set to be explored in the Fantastic Beasts series.
Speaking on Thursday, Rowling said future Fantastic Beasts films would show Dumbledore "as a younger man... at what I think was the formative period of his life."
Yet she refused to confirm speculation that the character would be seen in a gay relationship with Depp's character, simply telling reporters to "watch this space".
The author admitted she had been "in a kind of a bleak mood" as she prepared to travel to the US in the wake of this week's presidential election results.
But she said that working on the second film's screenplay during her flight had made her feel "a whole lot better".
Eddie Redmayne plays Newt Scamander in Fantastic Beasts, a "magizoologist" who travels to New York to continue his studies of magical creatures.
Fantastic Beasts and Where to Find Them has its UK premiere in London next week ahead of its release on 18 November.