The Cie'th, including monsters such as the Ghast, are created by fal'Cie from living humans. When people who have been made l'Cie are unable to fulfill their Focus, they are transformed into Cie'th. Places where fal'Cie were once active are often infested with large numbers of wandering Cie'th.
When fighting Ghast as the sidequest target in the Bresha Ruins, its Fira attacks are dangerous, and to ensure a 5-star rating, it is suggested the player develop Noel, Serah, and recruited monsters' primary role levels to about 20.
- Ghasts are first encountered in The Vestige and Lake Bresha in Final Fantasy XIII. The latter may be the reason it was added as a sidequest in the Bresha Ruins.