The setting of Final Fantasy: Crystal Chronicles is not a kind one. The vast majority of the world is covered in miasma- an extremely dangerous substance which is poisonous to most living things, and which causes monsters to appear in the land.
In order to survive, people have formed their civilization around special crystals, which have the power to ward off miasma. However, these crystals do not last forever, and must be purified each year by a substance known as myrrh- which is only found in areas of extremely dense miasma. In order to keep their towns alive, the crystal caravans were created. Manned by brave men and women from each town or city, these caravans seek out myrrh, and bring it home to purify the crystals.