Taunted and bullied in his youth, Jonathan Crane vowed to overcome his fears through the study of psychology and biochemistry on phobias and the nature of fear. Kicked out of the university he taught at for experimenting on human subjects, Crane adopted the identity of the Scarecrow, and armed himself with a specialized fear-inducing gas that makes a person's deepest phobia become a frightening reality. Scarecrow's ongoing reign of terror makes him one of Batman's most recurring and psychologically dangerous foes, if not the most dangerous. Scarecrow is, on certain occasions, more of a threat to Batman than the Joker. When The Joker took over Arkham Island, Crane was released to cause as much death and chaos as possible. Using this to his advantage, the Scarecrow tried breaking the mind of Batman again and again, only to fail. When attempting to poison Gotham City's water with his toxin, Crane was brutally mauled by the mutated criminal, Killer Croc. Seething with rage, Scarecrow exacted revenge on Batman and Gotham with his allies, the mysterious Arkham Knight and former assassin, Deathstroke. However, in the end, Crane's plan to break Batman's will failed, and he was forced to endure a dose of his own improved toxin. Reduced to a harmless shell, Scarecrow was left to suffer visions of bats.