Vapor

Alongside her brother Jimmy, Ann joined millionaire Simon Utrecht and pilot Mike Steel in an experiment to simulate the crash that gave the Fantastic Four their powers. Ann joined the group as she wished for more than merely fame, she desired great power. Aboard the unshielded spacecraft, the group located the cosmic storm area. Suddenly, they were bombarded with cosmic rays, and the turbulence caused Ann to stumble back into the life-support cylinders. Both her mask and the cylinders cracked, with a mixture of gases seeping into her lungs. The four were quickly rescued by Bruce Banner, who had witnessed the expedition. The ship crashed to Earth and the U-Foes emerged.

Now calling herself Vapor, Ann attacked Banner when he revealed he had been the one to return their spaceship. Soon, however, the U-Foes discovered that Banner was really the Incredible Hulk. After her teammates failed to defeat the Hulk, Vapor started to suffocate him, gloating as he was unable to hurt her physically. However, when Vector joined in the battle, he unintentionally deflected Vapor from the superhero and into her brother, X-Ray, causing Vapor's hydrogen form to light ablaze with fire. Her teammates attempted to save her, but she managed to regain her physical form and put out the fire herself.

Before the U-Foes could continue their battle with the Hulk, they started to lose control over their new powers. Vapor's physical body reverted back to mist and her atoms started to dissipate. In a last ditch effort, Vapor attempted to help Vector, but his powers deflected her and scattered her to the wind.

Alongside her teammates, she has had encounters with heroes including Hulk, the Avengers, Spider-Man, Crossfire, Puma, Darkhawk, and Portal.

During the Acts of Vengeance, Vapor attempted to kill the Scarlet Witch.

Vapor and the other U-Foes were recently recruited to serve Norman Osborn in his scheming, and have since joined the Hood's Gang. This arrangement ended after Norman Osborn fell from power following his attack on Asgard.