The Mutant Leader is a mysterious figure who commands the Mutant Gang. He has repeatedly singled out Commissioner Gordon and later vowed to also kill Batman. The Leader asserted the Mutants weren't criminals nor a gang but the future and law of Gotham City. A savage fighter, the Mutant Leader bested Batman in one on one combat in their first encounter. Just as he was about to impale Batman, the Leader was distracted by Carrie Kelley, a teenage girl dressed up as Robin. Batman used the brief window to toss an ampule in his face. The ampule released a super sticky black substance that binded to the Leader's face. As the Leader struggled, he succombed to asphyxiation and passed out. The Leader was arrested by the police and imprisoned in a jail cell at Gotham City Police Department headquarters.
The Mutant Gang vowed to raze Gotham City for this. The Mayor attempted to negotiate peace with the Leader but was almost immediately killed. Batman determined the only way to dismantle the gang once and for all was to defeat and humiliate the leader in front of his gang. Commissioner Gordon complied with Batman's plan and arranged for the Leader's cell doors to suddenly open. He was manipulated into taking the duct system out of police headquarters and wound up at the end of a sewage pipe at the West River and 40, in front of a gathering of the gang. Batman then knocked him into a mud pit, designed to slow him down. Batman methodically disabled the Mutant Leader then broke his right arm, right leg, and punched him out. The Mutant Gang lost their will and half were arrested while others split off into smaller gangs.