Agent Uno was part of unnamed government agency until her superiors chose her as the head of a new division, designed to handle superhuman and supernatural threats. She was free to recruit her own agents and field operatives. Her team was able to handle several threats, though the casualty of Rebecca Taylor disturbed her.
Her last case involved a battle with the Hand organization. Her team managed to kill the ninjas, but at the cost of civilian lives. Michael Badilino lost control at the sight, turning into Vengeance in front of her. Then burned the entire building and everything in it. Uno survived but with severe burns and a broken body. She was transferred to a hospital but nobody was able to identify her.
She got a second chance at life when becoming a host to the spirit of Megaera, one of the Furies, which allows them to go after the various Ghost Riders due to an age-old vow. When released from their vows, the Furies abandon their hosts. The broken body of Uno was again transferred away. She has not been seen or heard from since.
Agent Uno was created by Howard Mackie, and made her first appearance in Ghost Rider #52.