 As a result of surgical implants given to him by doctors employed by the Firm, the Scarecrow's body produces a mutated pheromone that affects the adrenal glands of people and animals (even crows) within twenty feet of him, causing a sensory overload which triggers a panic attack.The same pheromone affects the Scarecrow's own adrenal system, giving him superhuman strength and stamina.When the Scarecrow was raised from the dead by the sorcerer Stern, he became able to directly induce fear in his victims, and could survive and quickly recover from any injury, even typically fatal ones, as long as he was in the presence of the fear of others.