When the entity known as Onslaught first appeared, Iceman was chosen as one of his test subjects, along with Storm, Cyclops and Wolverine. They were pitted against a servant of Onslaught named Post, in a specific battle area of harsh environment to test the extent of their abilities. They won and were returned to the mansion. However, Iceman's chest had been shattered in his ice form during battle, making it impossible to change back to human form. He confronted Emma Frost and demanded to know what she did to his powers in his body and how to save himself. She refused to help since she knew that Bobby would have to do it himself. When he captured her with his ice powers, she telepathically showed him his insecurities. By confronting Opal and his father in her simulation, Iceman realized that Emma was right and managed to transform back to his human body with his chest fully intact.