As the Conquistador, Hidalgo hired many low-level villains (black masks), intending to use them to pull crimes at various pre-determined locations and plunge Astro City into chaos. Steeljack, who had been hired by the Conquistador, found out that he planned to kill all the black masks, triumphing in the public eye as El Guerrero. Unlike the other black masks who had discovered the Conquistador's plot, Steeljack was able to survive the Conquistador's attempts to kill him. Unable to secure any allies, Steeljack eventually confronted Conquistador on his own and just barely managed to defeat him. See Conquistador's Plot.
El Guerrero was the intended pseudonym, Hidalgo intended to return to the spotlight with after the events of the Conquistador's Plot played out and he came out a hero.
The Conquistador armor is super-strong, quite durable, and has a built-in oxygen supply. Both gauntlets possess an energy blast. The armor can distort its wearer's voice beyond recognizability, even altering it to precisely mimic the voices of others. Furthermore, it can project a hologram to disguise the wearer's face as another person's.