Fear Gas, also known as Fear Toxin, is the signature weapon used by the Scarecrow. Coming in a variety of forms (gas, liquid, powder) the substance induces involuntary and sometimes irrational fear in a victims' mind. Depending on the dosage amount and amount of time infected the gas has the ability to psychologically break the victim's mind; driving them insane.
A versatile substance, Fear Gas can be delivered through a variety of means through gas, darts, capsules, etc. His mask was made in order to enhance the effects of the hallucinogen while also acting as a gas mask to keep from poisoning himself.
- Player Characters with the Gadgets power can gain the Fear Gas ability which sprays out fear gas to paralyze victims with terror.
- In the Gotham City Sewers, the New Heroes must clear out canisters leaking Fear Gas from the sewers in order to proceed to the Scarecrow's lair.
- As he is with most chemicals, the Joker is immune to Scarecrow's Fear Gas.
- Due to his excessive use of psychological chemicals, Scarecrow has become unable to feel fear and claims that Batman is the only one capable of scaring him.
- After being dosed with a new strain of fear gas by Scarecrow, a strain that only affects women, Catwoman discovered that her primary fear is the fear of dependency.