Robert Downey Jr. has begun intensive preparations for his role as Doctor Doom in the upcoming Avengers films. Co-directors Joe Russo and Anthony Russo shared how seriously the former Iron Man is taking his return to the Marvel Cinematic Universe in the adaptation of the comics “Avengers: Doomsday.”

“He has a very intense process for building a character. He’s so immersed in it. He’s so passionate,” Joe Russo said. According to the directors, Robert Downey Jr. has gone so far as to “write a backstory and ideas for the costumes” for the villain. “I think he just loves really deep, three-dimensional characters, and I think he sees this character as a real acting challenge for him,” they added.

Meanwhile, Marvel continues to sink, and it remains to be seen what will happen next with this once-unsinkable franchise—whether Downey’s return in a new role can pull the studio out of its creative slump. We’ll have to wait and see what’s next.