The actor spent eight months exploring how a struggling stand-up comedian named Arthur Fleck becomes Batman's antagonist, the villain with a chilling laugh and a love of chaos. Preparing for the role involved losing quite a bit of weight, studying personality disorders and practicing the laugh over and over again.

"(It's) very difficult to distill into a soundbite," Phoenix said Saturday in advance of the world premiere of "Joker" at the Venice International Film Festival. The film is competing for the Golden Lion award at the prestigious festival before launching in theaters on Oct. 4.

The extreme weight loss — reportedly over 50 pounds — led to a kind of madness that helped him get ready for the role, as did a book breaking down the personality types of political assassins. But Phoenix wanted to create a criminal psychopath who wasn't easy to categorize.

"I didn't want a psychologist to be able to identify what kind of person he was," he said. "(I) wanted there to remain a mystery about the character."

And he was so nervous about getting the laugh right that he asked writer-director Todd Phillips to come to his place so he could "audition" a few, which apparently went on for an uncomfortable amount of time.

The character constantly evolved, even into the shoot. Composer Hildur Guðnadóttir's haunting score — which she began writing off the script — became a key motivator during the process. Phillips often played snippets on set to help set the tone.

"We were discovering new aspects about his personality up to the very last day," Phoenix said.

Sometimes the discoveries resulted in debates about whether or not to go back and reshoot.

On the long road to making "Joker" happen, that was par for the course. Phillips said in developing the script he and co-writer Scott Silver pushed each other every day to "come up with something totally insane."

The movie itself is a massive departure from the current mode of DC Comics films from Warner Bros, like "Wonder Woman" and "Justice League." It's not bound by the comics or informed by past portrayals ("This joker's goal was not to watch the world burn," Phillips said) but strives to be something entirely new.

"It was a hard movie for us to get made and to convince DC and the studio," Phillips said. "And in fairness the studio took a bold swing with the movie and let us do exactly what we wanted...there really were no rules and boundaries for it."

Phillips describes it as a character study in the vein of the 1970s movies he grew up with, such as Martin Scorcese's "Taxi Driver" and "The King of Comedy."

Set in the late 1970s and early 1980s, with New York playing Gotham City, his R-rated "Joker" is bounded by gritty realism. It's led to some early concerns about the violence that audiences can expect from the film.

Phillips said there isn't that much and they were "very careful" with how violence was used in the film.

"A lot of people think it is going to be a really violent movie," Phillips said. "Why it might affect you is we tried to paint it with as realistic brush as possible so when it comes it can feel like a punch in the stomach."

As for any thematic similarities to current events, he added that he thinks movies are "oftentimes mirrors of society but they're never molders."

Early reactions to the film have further fueled Oscar buzz for Phoenix.  to win one. The actor avoided acknowledging a question at a news conference in Venice about his prospects for winning his first Academy Award. He instead praised the creative process.

"I don't think I've ever had an experience quite like this one," Phoenix said. "The more unpredictable it was, the more inspiring it was."

But one thing Phoenix is sure of: He doesn't think of the Joker, or any of his characters, as "tormented." It's a word, he says, he only hears when he does media appearances for his films.

"I was interested in the light of Arthur for the lack of a better word," Phoenix said. "His struggle to find happiness, to feel connected, to feel warmth and love."

Director Phillips added that the man who becomes the Joker was looking for identity ... He thought he was put on this earth to make people laugh and bring joy to the world."