Late at night, I drive across the highway behind Mandalay Bay to the back lot of Vegas, where low-rise buildings house the contractors who build the elevators and the swimming pools. Inside a prefab warehouse on West Hacienda is a brand-new octagon. The desert air has been heated to more than 100 degrees. Rampage Jackson is lying down in the center of the octagon, where one of the several Brazilians in his camp works on his back. Juanito Ibarra comes over to me and explains what’s going to happen next.

“He’s going to go through the whole fight right now in the ring,” he says. “He’s going to raise his hands in victory. He’s going to internalize the movements and visualize the fight. Then he’s gonna lay down and see it all again in his mind.” The trainer looks more dour than usual, and winces when he climbs up the steps to the ring—the effect of two broken ribs that he suffered in camp.

“Son, do you know how talented you are?” he asks his fighter.

Ibarra’s assistant, Zach, presses Play on Rampage’s boom box, which blasts a rap song by Kane & Able. Rampage puts the hood of his black sweatshirt over his head, and then he steps out of his corner to take on his invisible opponent.

“Keep moving them big shoulders,” Ibarra calls out. The fighter drops to his knees and begins pounding on the ground with his fists.

“Three more minutes!” Zach calls out.

“Stay with him!”

Rampage launches himself through the air and lands on top of Griffin, battering the crippled imaginary fighter. “Make him face the cage,” Junior calls out. “Hips down. Too high. Put his face to the other side. Now punish.” Griffin escapes, and Jackson delivers a high, hard kick, followed by a whistling combination. The round ends with the challenger trapped against a stanchion, absorbing more punishment than any man could possibly bear.

“He’s going to get desperate now,” Ibarra warns. “He’s going to go very wild on you. He’s going to go back to all his bad habits.”

When the fight is done, Rampage lies in the center of the octagon and relives the action round by round, beads of sweat rolling down his black legs. All around him, guys are stripping off their workout clothes and talking about girlfriends and finding cabs to take them to nightclubs and hotels.

“I fought tougher guys under worse conditions,” Rampage tells his kickboxing trainer, Chris Reilly. He pauses for a moment in front of a larger-than-life cutout of himself in a white fur coat and sunglasses. “His shoulder is bad.”

“His shoulder is bad, his knee is bad,” Reilly says.

“I can’t go this long between fights,” Rampage says, pulling a face at the thought that it’s been 10 months since he last fought to defend his title.

“You did what your body told you to do,” Reilly soothes him.

The afternoon weigh-in on July 4 attracts perhaps 5,000 fans. The UFC’s star announcer, the comedian Joe Rogan, hasn’t shaved in days and is wearing a black stocking over his hair, which suggests that he has come to the weigh-in after pulling a stickup at the nearby In-N-Out Burger. Rogan, who is a former U.S. tae-kwon-do champion, started working as a UFC announcer in 1997, making him a holdover from the bad old days, when the stands were often populated by an unhappy scattering of drunks. He is familiar to viewers of more carefully sanitized mass entertainment from his roles as the fix-it guy on the NBC sitcom NewsRadio and the host of the NBC game show Fear Factor. He introduces the fighters. Rampage Jackson appears on a giant video screen to announce, “I don’t think Forrest can bust a grape,” to which the challenger answers, “I’ll take more pain than anyone.” Juanito Ibarra appears onscreen and predicts that his fighter will win, adding, “I’ll retire if Forrest Griffin beats Rampage Jackson.”

The lights go out, the crowd rises to its feet, and immediately the area is illuminated by the LCD screens on sure-shot cameras, palm-size video recorders, and cell phones casting a glowing patchwork of blue squares and rectangles from floor to roof. Rampage is greeted by loud boos from the crowd of young men in their 20s and 30s, dressed in black T-shirts decorated with gothic tattoos that they are too shy to wear on their skin. Nearly all of them are white. Jackson puts back his head and howls. “All you Rampage-haters, get used to it,” he shouts out into the roiling, blue-lit dark, rattling his chains. “I’m going to be your champion for a long time.”