Taunted and bullied in his youth, Jonathan Crane vowed to overcome his fears through the study of psychology and biochemistry. Kicked out of his university 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 fears become frighteningly real. His ongoing criminal reign of terror makes him one of Batman's most psychologically dangerous foes.

-Batman Wiki

Based on the version of Scarecrow from Batman: Arkham Asylum