Dressed in the robes of the Penitente order of the flagellent monks, Gabriel Santo is a strong believer of crime, and one of the most prominent members of the Penitente Cartel. The cartel's founder, a man using the alias El Penitente, tells Santo that by the end of the 21st century, crime will be the new social order. During a meeting of various crimelords and cartel associates, Santo welcomed Oswald Cobblepot as one of the cartel's newest and most powerful allies. Santo also told cartel associates that the cartel had hired Eduardo Flamingo to eliminate their primary enemies. However, the meeting was interrupted by Red Hood who killed many of the cartel members, and critically injured Santo.

Santo awoke in a hospital where he was confronted by Commissioner Jim Gordon. When Gordon asked Santo about the attack Santo merely told Gordon that Flamingo was coming on an "airplane from Hell". Red Hood later attacked Santo in his hospital room, who intended to kill him ironically, by pouring bleach into his I.V. tube. Fortunately for Santo, Batman and Robin arrived and stopped Red Hood before he could kill Santo. Batman and Robin were defeated and both captured, but Santo was spared as the bleach never actually reached his blood stream. Gabriel Santo's current whereabouts are unknown.