Crystal stasis

Crystal Stasis is a state a l'Cie enters upon completing his or her Focus in Final Fantasy XIII. The legend states that completing one's Focus and entering crystal stasis grants the l'Cie eternal life.

Nature
When a l'Cie completes a Focus their body turns to crystal and they become inanimate objects. However, they are not dead, but resting in what some call "crystal sleep". It is possible to recover from crystal stasis, whereupon the l'Cie comes back to life exactly as they were when they were placed in the stasis. It is unknown how aware a l'Cie is during their crystal sleep. In the end of the game Vanille and Fang appear to communicate their thoughts despite being in crystal stasis, however, the dialogue is only heard by the player.

The legend that completing one's Focus, and being encased in crystal, grants eternal life, originates from the fact that a fal'Cie can call its l'Cie back from crystal stasis to give their servant a new Focus. This way, as long as a l'Cie keeps completing his or her Focus, they can enter crystal stasis multiple times and be revived to live again once their fal'Cie needs their assistance. However, this only leads to a life in slavery under the fal'Cie master.

During the game it is demonstrated that completing a fal'Cie-given Focus isn't the only way to enter crystal stasis: the Pulse legends state that the Goddess stopped Ragnarok during the War of Transgression by placing the Ragnarok's l'Cie in crystal stasis prematurely. How accurate the legend is, is up to player interpretation. Cid Raines can also be observed to enter crystal stasis despite having outright defied his Focus. It appears that the l'Cie might have the power to overcome their fal'Cie-given Focus and give themselves a new one. Whether or not entering crystal stasis was done on Cid's own accord or not, his fal'Cie is still able to revive him from the stasis and give him a new Focus. The case with Vanille and Fang is less clear; their fal'Cie, Anima, did not revive the pair from their crystal sleep for 500 years, and it is unclear whether they were revived by natural methods (the effect of crystal stasis simply running out on its own due time), or if they were taken out of their crystal sleep by an outside force.

At the end of the game the entire party, as well as the world of Cocoon, crystallise. Apparently due a prompt from Vanille, Lightning and her friends come out of crystal stasis almost immediately after having been placed in it. It is unknown how Vanille has the power to release the others from the stasis, although it might have been the Ragnarok's doing the first place. Serah and Dajh also are released from their crystal sleep and are reunited with the party. Fang and Vanille, however, stay in crystal stasis, perhaps indefinitely. The game's strategy guide appears to suggest that Fang and Vanille did not come out crystal stasis like the rest because they crystallised themselves wilfully.