Born to a poor worker's family in Buenos Aires, his brother was slain by the military during the Cordoba Coup. During the cleansing of Argentine society, Sebastian’s parents were taken in the night and disappeared. Sebastian didn't follow in his radical parents' footsteps. In fact, he rejected their values and politics because he hated the lower class and wanted out of it himself. He was good with business and forged an alliance with the dictator who had his family killed. Sebastian was soon out of the poor class and one of the rich.
But he realized that he lacked real power. He learned that a woman secured the power of a plant god, the Cheetah. Ballesteros bargained with the god and managed to persuade him to take him as Urzkartaga's avatar. Urzkartaga believed that current host Barbara Minerva was too weak and that with Ballesteros he would make a strong conduit.
Ballesteros was the one who made Vanessa Kapatelis into the cyborg Silver Swan. After the new Silver Swan's first encounter with Wonder Woman, Ballesteros had Vanessa kidnapped again and added more cybernetic implants. Then he sold her to Veronica Cale. But Sebastian made the mistake of not making sure the last Cheetah was dead, and she came after him. Minerva had a chance to kill Ballesteros and took it. Now his blood feeds Urzkartaga.
After the company-wide reboot, Sebastian Ballesteros was erased from existence. However, "Sabrina Ballesteros" was used as an alter-ego by Barbara Minerva.