When a rogue member of the Nova Corps unlocked the full potential of the Nova Force without having to become a Centurion, he created a new branch of Black Novas designed to be vigilantes. When Jesse Alexander joined the team, he had all corrupt members arrested and turned the team into a black ops unit.
To Sam Alexander, the Black Novas were only stories, figments of his father, Jesse's, imagination. He believed this, until he became one. After finding and wearing his father's Nova Helmet, Sam realized he was telling the truth and began his search for him.