Oxygen

Oxygen is a gas within the Earth's atmosphere. It is necessary for human's and other lifeforms on the planet to breathe.

Once, a space mist entered the Earth's atmosphere, where it was transformed into shamonite due to it's strange effects from the oxygen. It is invisible to the naked eye, just like the other gases that make up the atmosphere.

Appearances/References
Super Friends
 * Season 1: The Shamon 'U'