Fabula Nova Crystallis is the name of the mythology on which several episodes of the Final Fantasy series are based, including those bearing the number XIII. The name basically means "the new tale of the crystal" in Latin, a language that is frequently found in various projects (including the title for Versus, which means "change of direction").
The logos of the Fabula Nova Crystallis project have all been designed by Yoshitaka Amano. Three of them have a blue circle whose meaning is currently unknown, although fans theorize that it could represent a crystal, the key element of the saga, while other believe it represents a moon, another element that held a great importance in some episodes of the Final Fantasy franchise. That said, the absence of this circle in the logo of Final Fantasy XIII remains quite very enigmatic.
“One myth,
countless stories
FINAL FANTASY XIII
The New Tale of the Crystal
Like the light that shines through the Crystal,
the universe shines with multicolored content.â€
—Online Description
The concept of the Fabula Nova Crystallis is that of a mythology used as the basis of the development of different games. While none of these games take place in the same universe, they all share the same myths, with the Crystal being at the center of the story. In short, by using the same base material, several developers have imagined different elements including the universes, intrigues and unique characters. However, while these games share the same starting point, they each follow their own path.countless stories
FINAL FANTASY XIII
The New Tale of the Crystal
Like the light that shines through the Crystal,
the universe shines with multicolored content.â€
—Online Description
  
This concept, already attempted with the Compilation of Final Fantasy VII for example, is a perfect illustration of what Square Enix defined under the word "polymorphism", with several projects revolving around a basic idea. In the case of Fabula Nova Crystallis however, the projects are not consequences of each other. It is not necessary to play every single one of the game for the maximum enjoyment and understanding of the nature of the mythology, the latter being simply a starting point. On a financial level, the globalization of preproduction also allows the company to save money, an aspect that is far from negligible considering how much it costs to develop PS3 games.
The logos of the Fabula Nova Crystallis project have all been designed by Yoshitaka Amano. Three of them have a blue circle whose meaning is currently unknown, although fans theorize that it could represent a crystal, the key element of the saga, while other believe it represents a moon, another element that held a great importance in some episodes of the Final Fantasy franchise. That said, the absence of this circle in the logo of Final Fantasy XIII remains quite very enigmatic.
 
Moreover, the logos drawn by Amano for each project take a different color, FFXIII being blue-green, Versus XIII being marine blue and Type-0 being attributes a reddish-maroon color. These different colors once again emphasize the concept of Fabula Nova Crystallis, incorporating the different colors created when light reflects through the crystal.
