H2S

H2S is a poisonous gas that appeared on Punk Hazard.

Effects
It is the formula for hydrogen sulfide, a poisonous gas that can be very harmful to tissue in the body if it is contacted in any way. It can also be found in a liquid or gel-like form.

While it was in compressed form of gel, the poison was fast moving, and was capable of killing victims when it completely covers them, and causing immense burns and pain even when simply being touched. The liquid form of H2S is also highly volatile when set aflame directly.

When added with a special "bait" to the gelatinous form of the chemical, the H2S transforms into an even more deadly gaseous form, which spreads at an incredible speed, and petrifies any organic victims that are caught within it as it enters their skin and body, turning the recipients into a crude state similar to stone. However, there is still an unspecified way to counter the effect and rescue a person, even when they have been petrified.

History
Four years ago, Caesar Clown triggered H2S gas to be leaked out on Punk Hazard as retaliation for being fired. This devastated the island's ecosystem, killing many forms of life on it, but he remembers the fact that some of them survived. Caesar then accumulated the gas and compressed it, thus creating his artificial creature and weapon of mass destruction named Smiley. It is one of the chemical compounds that Caesar uses as a poisonous gas.

When Caesar decided to debut his newest gas weapon to brokers across the world, he lured Smiley with a piece of "bait" in the shape of a giant candy, which, when devoured, had Smiley regress back into his original gas form, with the bait's ingredients converting the H2S gas compound into an even deadlier form, decimating many of Caesar's centaur subordinates.

When Caesar was being cornered by Luffy to no end, he decided to let the H2S flow into the lab and absorb the petrifying smoke into his body, which greatly enlarged him. He then claimed that two peaceful countries already wanted to purchase the H2S gas due to seeing the potential, and poured the gas onto his underlings as an exhibition for his criminal underworld spectators.

After Caesar was defeated, G-5 marines tortured the captured scientist and forced him to reveal the weakness of the gas, thus giving them a chance to save the victims.