Chain Lightning was a Metahuman woman with multiple personality disorder who has the power to absorb and dispel electricity in the form of lightning bolts. As such, she can cause the Marvel Family to revert to their non-powered forms if she attacks them with enough of a charge. Her first encounter with the Marvel family was with Mary Marvel. Mary eventually defeats Chain Lightning and she is taken away by the police.
Amy was born with the mutant power of absorbing electricity, but never learned uses for her power until a mysterious benefactor gave her a powersuit that let her channel the electricity she stored. At about this time she began suffering from multiple personality disorder. The four personalities consisted of her "actual" persona of Amy, the embittered Amber, her inner child, and her id. She battled Captain Marvel, Jr., but was defeated and sent to S.T.A.R. Labs for treatment. Due to the nature of her powers, Amy can cause the Marvel Family to revert to their non-powered forms if she attacks them with enough of a charge.
Captain Marvel, Jr. kept in touch with Amy, visiting her at S.T.A.R. Labs on a regular basis. She felt very attached to him after these visits.
Amy still going by Chain Lightning joined the the Society. She was assigned to the Frisk Nuclear Power Society here captive hero Mary Marvel kept powerless by Society member Vault.
Arsenal of the Outsiders infiltrated the Society disguised as Deathstroke and gained access to Frisk. Arsenal and the Outsiders freed Mary Marvel, and after Amy saw that Captain Marvel, Jr. was a member of the Outsiders, so she switched sides and helped them. Chain Lightning plan to help was to blow up Frisk's reactor with her electrical powers, but fortunately the Outsiders and Society members cleared out before the plant exploded.