When lawyer Jennifer Cassidy was representing her client, she had no idea that he was possessed by a demon. The demon fired a blast of hellfire at her and critically injured Jennifer. No medicine or treatment was helping her and to save her the doctor used an experimental gamma-irradiated blood transfusion. Jennifer found herself transformed into a green-skinned warrior woman with devilish horns. Now super-humanly strong and able to fire blasts of gamma-powered fire from her trident, Jennifer uses her powers for good as the She-Devil.