Rachel Leighton was born in Austin, Texas. She was once a part-time sales clerk at a boutique, but later became a mercenary. In "Captain America" vol. 1 #319, she reveals to Captain America that she has a brother and that when she was younger was introduced by him to the super-criminal known as the Trapster. In exchange for weaponry that the Trapster provides her with, Leighton suggests that in return she prostitutes herself to the criminal. One of the members of the original Serpent Society, Diamondback was a seductively sly woman with expertise in hand-to-hand combat, being trained by Anaconda at Taskmaster's academy. Her gimmick was that she threw acid-laced or poison-tipped diamonds at her enemies. After her first confrontation with Captain America while on assignment to find MODOK, she was instantly smitten. Diamondback was assigned to take Captain America into custody from the Porcupine, but was reluctant to attack, concentrating her efforts on Porcupine instead. She later attempted to form a partnership with Captain America to locate the Scourge of the Underworld.