The inner sanctum is dead quiet. The offices of just five executives—each with its own balcony—take up the entire sixth floor. It’s hard not to be intimidated. Indeed, many people who have crossed paths with Diller in recent years warned me not to take it personally if he came across as belittling. In fact, he is disarmingly polite, almost soft-spoken. He is smaller than you would expect but gives off an air of bottled intensity.

The Diller legend has been laboriously constructed, put together piece by piece. There were the nights at Studio 54 in New York 30 years ago, when he hung out with Warren Beatty, Calvin Klein, and Mike Nichols. He was named ABC’s programming chief at the age of 26. At 32, he was offered the chairmanship of Paramount. From there he went on to launch the Fox network. The lasting impression is that for a while, Diller was the ultimate Hollywood mogul. “In the flesh, he was power incarnate,” producer Dawn Steel wrote in her book They Can Kill You but They Can’t Eat You. “He was the sexiest man I’d ever met. He handled power differently from anyone I’d ever known, in this very complex, sexual way.... You couldn’t not look at him.” (VIDEO: Watch Diller explain how he broke into the entertainment industry with no college degree.)

Diller was always a hybrid, equal parts business guy and showman. Like his old friend David Geffen, with whom he worked in the mailroom at the William Morris Agency, he is addicted to the deal. At Paramount, he cooked up tax-advantaged deals structured in ways that other moguls couldn’t understand. He’s bought and sold more companies than Rupert Murdoch himself.

More than that, he was making the connections and building the reputation that would last him throughout his career. Some of the most powerful executives in Hollywood in the past 20 years—Michael Eisner, Jeffrey Katzenberg, Dawn Steel, and producer Don Simpson—worked for him at Paramount, where they became known as the Killer Dillers. At Fox, he teamed up with Murdoch, who remains a close friend. When Murdoch sealed the deal to buy the parent company of the Wall Street Journal in August, Diller hosted a party for him on a yacht anchored off Manhattan.

“Sure, he’s a bundle of contradictions. But most people—most people I like, anyhow—are,” says Kurt Andersen, a media veteran who has done business with Diller over the years—including, most recently, the launch of the website VeryShortList.com. “If you’re famous, your public persona can often be reduced to a noncontradictory cartoon. But with Barry, his contradictions are just more vividly apparent than most.”

Diller has also consistently cultivated strong relationships with the media, providing financial support for The Charlie Rose Show, for example. As a result, he’s been a repeat guest on the program. He’s also bankrolling a news-aggregation website headed by former New Yorker and Vanity Fair editor Tina Brown. “He expresses himself better than anyone I know in business,” Brown says.

“Take him on at your peril,” warns Howard Stringer, the chairman of Sony. “People in the press are afraid to ask him a stupid question because the entire world will know in 30 seconds how stupid it is.”

Diller has used his formidable social and media networks to help wall off his public persona from his business one, an invaluable trick in tough times. Social chronicler Dominick Dunne—who sat at the same table as Diller at an awards ceremony only weeks before Diller’s trial was set to begin—makes that clear. “You never would have had a clue from his conversation or his speech that he was dealing with big problems in his life,” Dunne says, referring to the fight with Malone. “I admire him for that.”

Diller crafts his private persona as carefully as his public image. The social life on display is that of a bon vivant who swans around New York and Hollywood with his wife of seven years, fashion designer Diane von Furstenberg. Diller owns one of the world’s largest private yachts, the 305-foot-long Eos, and hosts a lavish pre-Oscars party at his home in Beverly Hills’ Coldwater Canyon. But in fact, Diller is a fiercely private man who spends much of his time while in New York at the Carlyle Hotel. Few know, for instance, that his brother was murdered in California in 1975 after a number of run-ins with the law. And though speculation about Diller’s sexuality has swirled for years, he has never addressed the topic.

There's no denying that Diller is an extremely smart man. He speaks in well-constructed paragraphs. It's received wisdom in media circles that you don’t tangle with him. There’s the story about the time he threw a videocassette at someone’s head and the one about his making a senior executive cry. While his supporters go to great lengths to cast his prickliness in a positive light, the truth is that the guy can be ruthless. “He’s got elephant balls,” David Geffen once told a reporter.