Oxygen Destroyer

The Oxygen Destroyer (オキシジェン・デストロイヤー Okishijen Desutoroiyā) is a fictional weapon of mass destruction invented by Dr. Daisuke Serizawa and used to kill the original Godzilla in the 1954 film, Godzilla.

Origins
The Oxygen Destroyer was the invention of Dr. Daisuke Serizawa. Having devoted his studies to the element oxygen, Serizawa accidentally stumbled upon a volatile and deadly chemical reaction. Though horrified by the destructive potential of his discovery, he nonetheless continued his research, optimistic that some beneficial outcome could be produced from it.

Design
The Oxygen Destroyer is a heavy device composed of a metal capsule with a glass central chamber. Within this chamber is a second capsule attached by rods at either end. Contained within the capsule is a large amount of what would be later known as Micro-Oxygen, the weapon's payload. Numerous gauges and pressure meters are present on the larger capsule. To operate the Oxygen Destroyer, the two ends of the larger capsule have to be pushed inwards. This causes the rods securing the inner capsule to pull apart, releasing the Micro-oxygen within.

Godzilla: King of the Monsters
The schematics for the Oxygen Destroyer in Godzilla: King of the Monsters

As the USS Argo battled with Monster Zero near Isla de Mara, Monarch was contacted by Admiral William Stenz, who asked them to evacuate immediately. He informed them that the military had developed a prototype weapon specifically to combat the Titans: the Oxygen Destroyer. The chemical weapon, attached to a missile, was already inbound to the area and would kill every organism within a five-mile radius. After dispatching Rodan, Monster Zero turned his attention to the Argo only for Godzilla to erupt from the sea and drag Monster Zero down with him. Godzilla seemed to be winning the fight, keeping Monster Zero under the water and even tearing off one of his heads, but the Argo was forced to withdraw as the Oxygen Destroyer prepared to impact. As soon as the warhead struck the water, it produced a colossal mushroom cloud emitting an eerie green glow. As the smoke cleared, dead fish began floating to the surface of the water.

Suddenly, the now two-headed Monster Zero flew out of the water seemingly unaffected by the blast and made his way to the Isla de Mara volcano. Shockingly, he near-instantaneously regenerated his severed head and was none the worse for wear. Godzilla, however, was seriously injured by the blast and began to sink into the deep, his vital signs rapidly decreasing. Finally, Dr. Rick Stanton informed his colleagues that Godzilla was dead. The military had apparently killed its best hope for defeating Monster Zero, or "Ghidorah" as he would subsequently come to be known. Fortunately, Godzilla was not killed by the Oxygen Destroyer and had retreated to his lair to feed on radiation and heal. Monarch's Dr. Ishiro Serizawa gave his life to accelerate this process by detonating a thermonuclear warhead next to the resting Godzilla, the radiation immediately rejuvenating him. Godzilla was revived to fight another day, and with the assistance of Mothra triumphed over Ghidorah.

After Godzilla's victory, the waters surrounding Isla de Mara were still contaminated by the Oxygen Destroyer, leaving the locals unable to catch fish. They caught something else, however: Ghidorah's severed head. Alan Jonah and his men traveled to Mexico to examine it; upon doing so, Jonah simply said, "We'll take it."

Mechanisms
The device works by activating a chemical stored within its spherical center, which causes the center to split in half and open. Once released, the chemical (later dubbed Micro-Oxygen by Kensaku Ijuin) reacts violently with the water, isolating oxygen molecules and splitting them. The molecules are then liquefied. This means that any organism exposed to the chemical will first suffocate from the lack of oxygen, and then disintegrate. Depending on the amount of the oxygen destroying chemical released, the body of the victim will either be eaten down to the bone or destroyed completely. When used to its full potential, the Oxygen Destroyer will leave no remains. According to Dr. Ijuin, if the Oxygen Destroyer had been used on land, it would have turned Tokyo into a cemetery. Creatures that thrive in anaerobic environments, however, such as the Precambrian crustaceans that became Destoroyah, can actually be empowered by the Oxygen Destroyer's chemical reactions and mutate to incorporate Micro-Oxygen within their bodily processes.

In Godzilla: King of the Monsters, the basic shape of the device itself is evidently mostly unchanged, as seen on a digital schematic. However, the Oxygen Destroyer is now fired while attached to a missile. Upon striking the water, rather than simply causing a violent chemical reaction, the Oxygen Destroyer produces a powerful explosion that creates a mushroom cloud. The blast does not reduce its victims to skeletons, though it effectively kills all sea life nonetheless. The explosion given off by the device was sufficient to seriously injure and weaken Godzilla, while the extraterrestrial King Ghidorah proved immune to both the blast and the chemical itself.