Jerome Valeska was a deranged, mass murderer and anarchist. He was the more vengeful and chaotic twin brother of the obsessive and methodical anarchist mastermind, Jeremiah Valeska.
Born and raised in Haly's Circus, Jerome murdered his mother roughly at the age of eighteen, which led to his arrest and incarceration at Arkham Asylum. Following a breakout with other inmates orchestrated by Theo Galavan, he became the leader of The Maniax and wreaked chaos upon the city. This later led to his betrayal and murder at Galavan's hands, although his death brought about an underground movement devoted to him and his way of thinking.
Jerome was later resurrected from the dead by a follower, allowing him to once again reign terror upon Gotham City. Jerome grew an obsession with Bruce Wayne and the idea of killing him but was stopped and was re-incarcerated in Arkham once more. After Sofia Falcone defeated Oswald Cobblepot, he got sent to Arkham where he met Oswald. Jerome was shown to have full control of Arkham and could escape at any time, however, he says that he wants to make a show of his escape - further displaying the extent of his 'showman complex'. However, he would soon escape with his new allies and fellow inmates Jervis Tetch and Jonathan Crane. This alliance later evolved into the Legion of Horribles, reinforced with Oswald Cobblepot, Mr. Freeze, Firefly and Solomon Grundy, which operated with the goal to drive Gotham City into madness according to a plan by Jerome, while he promised the other members to rule the city after its downfall. On Jerome's request, Scarecrow therefore developed the dangerous Laughing Toxin that Valeska wanted to spread across the city with a blimp. Shortly after, it came to an ultimate showdown between Gordon and Jerome on the top of a building, in which Valeska got shot, only for him to fall, leading to his life hanging in the balance, as he was able to hold on to a pipe sticking off the building. Even though Gordon reached out and tried to save Jerome, the young villain stated that his legacy will live on in Gotham City before letting himself fall to his second and final death instead of having his life saved by Gordon, laughing all along the way down.
However, Jerome knew that his terror over Gotham did not end with his death, which made it easier for him to accept his fate and die with the confidence that his plans will succeed in the end. Though the potential disaster from the blimp filled with laughing gas was averted by the Penguin, Jerome's ultimate revenge was actually more inconspicuous in form of a jack-in-the-box filled with a special laughing gas that he had his allies deposit in Jeremiah Valeska's secret bunker. When Jerome's brother unsuspectingly opened it, he got sprayed by the laughing gas and as a result, Jeremiah began to act out, smiling and laughing unnaturally as the gas turned his skin pale white and his lips red.
