The Miasma Stream (瘴気ストリーム, Shōki Sutorīmu?) is a barrier which hinders travel between regions of the Final Fantasy Crystal Chronicles continent. Caravans without a Chalice or a Chalice imbued with the wrong element suffer drastically in a Miasma Stream, not even able to advance. Moogles, like Stiltzkin, seem unaffected by them, however. Miasma Streams can be found separating Tipa Peninsula, Ironmine Downs, the Vale of Alfitaria, Veo Lu, the Plains of Fum, the Rebena Plains, and the Abyss.
The miasma stream fluctuates in intensity as one tries to cross it, the wind growing steadily until it pulses, finally calming as the caravanner is pushed out of the miasma stream. The final stream is of the mystery element, which requires a quest to obtain.
The Miasma Stream appears as a stream of darkness with several monsters in that area. After the player has defeated all monsters in the vicinity, using Layle's Crystal Bearer powers they must then close the Miasma Stream. It should be noted, that this is the first time players will not get hurt if they do not close the Miasma or Miasma Stream. It should also be noted, that this is the first Miasma to appear not in barrier form. Each time the player closes it, a Myrrh Fragment that increases Life points by 1 will appear.
Early medical theories predating the discovery of microorganisms often associating foul air, called miasma, from crowded conditions or rotten objects as a cause of disease.