Spark originally joined the Legion as a replacement for her twin brother Live Wire, as their planet, Winath decided to choose her rather than Garth, who had been classed as a runaway. Eventually, the "one member per planet" restriction was lifted, and he rejoined.
She was one of the members stranded in the 21st Century for a time as a result of the Emerald Eye's machinations. While there, she travelled into the Source, which replaced her electrical powers with anti-gravity ones (although she did not change her codename). Upon returning to her native 31st Century and reuniting with her brother, however, she began to experience debilitating headaches when using her powers, which were diagnosed as psychosomatic. Apparently, she couldn't handle having different powers to her brother. In a desperate attempt to restore her old powers, she returned to Korbal, the planet where she and her brothers originally gained their powers after being shocked by a "Lightning Beast" (which, at the time, had left them in a coma for months). Her altered genetic structure left her unable to take another blast however, and she was killed. Shortly afterward, her brother and some of their teammates, who had followed her, arrived. In grief, he let off a huge blast which temporarily revived her, and Doctor Gym'll theorised that a greater blast could properly revive her & restore her electical powers. By channelling a huge amount of atmospheric electricity, Garth succeeded. Shortly afterward, she became romantically associated with fellow Legionnaire Chameleon, who had a longstanding crush on her.
Later, the Legion was disbanded after the apparent death of several of her teammates (including her brother and Chameleon) and she returned to Winath. However, when these teammates returned, Garth was not among them, having apparently sacrificed himself so the rest could return home. After Chameleon broke this news to her, she apparently did not resume her relationship with him. She briefly took the name Live Wire after this, but shortly before his return, she was convinced by Kid Quantum that she'd be better honouring her brother by being herself
Powers and abilites
Spark has the ability to generate electricity, and direct bolts of it accurately (the exact mechanism in her power which prevents the bolts taking the path of least resistance to Earth is not understood), which she commonly refers to as "lightning."
She briefly possessed the ability to reduce objects' density, but has shown no sign of this since the restoration of her electrical powers.