Little is known of El Dorado's past, we do know however that he is a magical luchadore with the purpose of breaking the mystical chain between fathers and sons of El Muerto's family and their ancestral power that comes with a magical mask.
Peter David created El Dorado for Friendly Neighborhood Spider-Man #7 alongside Roger Cruz.
Major Story Arcs
For More Information: Masks
When Juan-Carlos fails to fight El Dorado, El Dorado killed Carlos' father and tells the boy that he has ten years to train and travel before he must defeat a masked hero in hand to hand combat before removing their mask. When the ten years pass, Carlos - now El Muerto - is defeated by Spider-Man and so El Dorado comes to New York to execute him. However, as El Dorado stands over El Muerto in his hospital bed, Spider-Man arrives to save him. Though initially unable to break through El Dorado's armor, Spider-Man eventually manages to use a chemical mixture to destroy part of it and punch El Dorado through the hole into a cupboard. Defeated, El Dorado teleports away before Spider-Man or El Muerto can get to him.
Powers and Abilities
El Dorado's main power appears to be super strength coupled with fighting abilities. His armor also supposedly provides him with invulnerability to magical and scientific powers - though it was damaged by a chemical solution created by Spider-Man. He also has super hearing and was able to track Spider-Man in what might be a similar way to Spider-Man's spider sense. Also, he showed himself able to teleport himself even when injured after being hit in the chest by Spider-Man.