After having been busted out of Arkham Asylum, Jerome was offered the chance to wreak havoc in Gotham in the Season 2 opening story arc Rise of the Villains. As the leader of the Maniax, Jerome terrorized the whole of Gotham. Although he was betrayed and killed by his boss Theo Galavan (who wanted to be seen as a hero to the city), Jerome left a legacy leading to some citizens to follow his example, causing a fanatical cult to plot his resurrection. A year following his death, Jerome's reanimation was a success and Jerome ignited a bomb which blew up Gotham's power grid, causing a city-wide blackout and plunging the city into darkness and anarchy.
He was portrayed by Cameron Monaghan, who is best known for portaying Ian Gallagher on the Showtime comedy-drama Shameless.