Fear Toxin was a deadly gas used by Scarecrow. Although for most of his villainous career, the Scarecrow had kept the normal Toxin relatively the same, as the only one who was truly invulnerable to it was the Batman. At the end of 2012, however, insanity struck the Scarecrow worse than ever and he created a poisonous new strain. This strain was so deadly that it even managed to effect the Batman. It was almost launched on to the entire city, but due to the Batman, who later gained immunity, the rest of Gotham City was saved. These main strains of Fear Toxin, although normally unchanging, had several cures.
The Fear Toxin caused a decrease in sertonergic neurons of the hypothalamus to produce hallucinatory effects. The effects of the Fear Toxin were less intense when absorbed through the skin rather than the lungs. First contact with the epidermis caused a burning or freezing sensation. The nerve receptors in the epidermis soon began to react, causing rapid synaptic and neural misfires. The toxin then effected the brain, stimulating the amygdala and dorsal hippocampus to trigger various specific fear memories. It brought forth the most deep-seated fears and phobias and intensified them. It also manifested as a hallucination of a specific moment of intense trauma or stress, stretched to an interminable length. The strain on the mental state of the afflicted resulted in a severe physical response, which was known to include conniptions, catatonia and cardiac arrest.
When delivered to a person already dosed with the Contentment Sedative, the Fear Toxin was known to result in a more "pure" reaction as well as fundamentally altering the norepinephrine production of the brain. This could then be "harvested" to produce fuel to make more fear toxin. Due to this, Fear Toxin could be used to recreate itself in extremely large quantities.
Fear Toxin-Venom Compound Edit
After his plan to take down the Batman was foiled, a desperate Bane joined forces with Scarecrow to produce a Fear Toxin that contained the side-effects of Venom. This rendition of the Fear Toxin was not a new strain, but rather a completely different compound bearing the same title. This compound could only be taken out of one's system if it was burned out, though to one effected by Venom beforehand it enhanced their mental senses. If not removed, this compound was fatal. A cure was later developed.
Cassandra Strain Edit
The Cassandra Strain was a Fear Toxin developed by Scarecrow to finally be able to take down the Batman. Nonetheless, it was ineffective and simply retreaded most of the effects of previous compounds. It was later discovered to plant seeds of fear that would emerge in one's subconscious, taking over during dreams and blackouts.