Final Fantasy Infinite
You remove a thick book from the shelves, blowing dust from the cover and spine, the gilded letters shining once again: “The Crystallis: A Guide”
The Crystallis (singular: Crystallis) are a collection of massive crystalline gems, embedded into the earth. They have the unique property of generating a bubble that cleanses and wards off the toxic Miasma that pervades the world.
Smaller pieces of the Crystallis can be grown and harvested with a specific ritual, providing a much smaller area of clear air, proportional to the size of the crystal. A crystal roughly the size of a man’s fist will create a safe area larger than a covered wagon.
Legends from the ancient days tell of the Crystallis being sentient, and even working alongside the sentient inhabitants of the world. Sadly, those days have passed, and the Crystallis have remained silent as far back as we can remember.
Information added by Monty Karonet
The Crystallis were the literal incarnations of law and order, created by some higher powered deity. They, and the Espers, were responsible for the creation of the world of Gaia and all of the inhabitants therein.
Wishing to rule over the creatures they created (since they could not rule themselves, as the Crystallis saw), they began to forcibly convert beings into their servants. This action sparked the Crystal War, which ended with one continent poisoned with a noxious gas, another devoid of life or the potential for it, and a third in an unknown state.