Uno is raised from childhood by a secret organization named the Q Society to be the champion of the Aztec god Quetzalcoatl to battle their enemy, the Aztec god Tezcatlipoca. He is given a magical suit of armor that bestows many abilities, complementing Uno's peak human mental and physical abilities. After his training is completed, he enters the United States and assumes the identity of recently deceased physician Curt Falconer. Aztek later joins the Justice League, but resigns when it is revealed that one of the mysterious benefactors of the Q Society is supervillain Lex Luthor. He is later blinded helping the League save the Earth in a battle against the planet-destroying machine Mageddon (apparently the Tezcatlipoca that the cult was referring to all along). Aztek ultimately sacrifices himself to allow Superman the chance to destroy Mageddon/Tezcatlipoca, during the World War III story arc.
A new version of the character appeared in Justice League of America vol. 5 #20; instead of being Uno/Curt Falconer, the new hero is Nayeli Constant. She was a software engineer in Austin, Texas who was startled by the Aztek helmet bursting into her window and telling her about the millennia-long war against the dark god Tezcatlipoca. She decided to accept the role of the new Aztek and modified the armor to suit her purposes; eventually finding her way to Vanity after The Ray left the city to join the Justice League of America. When he returned from a mission, the two encountered one another and briefly argued about who should protect the citizens of Vanity but they teamed up to stop a criminal and decided that the city could use both heroes.
Aztek appeared in Justice League Unlimited.