Scarecrow is Jonathan Crane, formerly a psychiatrist and university professor, Crane has been tortured, humiliated and intimidated ever since he was very young and in much of his life.
As an adult, through his studies, he became obsessed with the nature of fear, and in controlling through psychology and biochemistry all human phobias.

Creating the Scarecrow's identity, he developed his greatest weapon, the Scarecrow's Gas, a fear toxin capable of generating in its victims the deepest phobias by hallucinations.
In Arkham Knight, by terrorist means managed to cause a mass evacuation of Gotham City; and allied with other crime bosses, dominated the city and created a land without law. It is the main antagonist of the game.