Eidolith Eidolith is a type of crystal from " Final Fantasy XIII " and " Final Fantasy XIII - 2 " . They are granted to l ' Cie upon defeating an Eidolon sent by the goddess Etro which allow them to summon said Eidolon . Each person ' s eidolith is of unique color and shape . In both games , the eidoliths are used for achievements and trophies images . Appearances . " Final Fantasy XIII " . Lightning and her new allies of circumstance are chosen by the fal ' Cie Anima and branded by the god Pulse as l ' Cie . The party descends into an alternate realm where a dark figure ( identified as the god Pulse in " Final Fantasy XIII Ultimania Omega " ) emerges out of a crystal and strikes the party somewhere on their bodies ; where " touched " by the god Pulse , the l ' Cie have the brand of l ' Cie , but furthermore , this act appears to grant the l ' Cie their eidoliths . This allows them to use magic and learn new abilities via the Crystarium , making them far more powerful than regular humans . Whenever the l ' Cie cast magic they channel it from the eidolith in their body . The eidoliths are not obtained as key items in the inventory before the l ' Cie has tamed their Eidolon . The item descriptions describe eidoliths as crystals that house the souls of the l ' Cie ' s respective Eidolons . It appears that even though the l ' Cie possess their crystals ever since having become l ' Cie , they are not " aware " of their exact existence before having summoned their Eidolon for the first time . During times of conflict the goddess sends Eidolons to the l ' Cie ' s aid and the l ' Cie summon their Eidolons by manifesting the image of their eidolith and shattering it . For example , after the party ' s airship is destroyed and they are sent falling through the air toward Gran Pulse , Fang manifests her eidolith and throws it in the air ; when Lightning shoots it with her weapon , Bahamut is summoned . " Final Fantasy XIII - 2 " . Even people who have never been made l ' Cie can progress through the Crystarium and thus use magic due to the soil of the earth having absorbed crystal dust on the Day of Ragnarok . The Crystarium for the party members in " Final Fantasy XIII - 2 " looks different than it did in " Final Fantasy XIII " , however , and the character ' s personal crystal is no longer in the center of the system . The notable eidolith is that of Caius Ballad , which he keeps in his sword , as opposed to it being implanted into his body . Caius used to be a l ' Cie who was saved by goddess Etro , and can perform incarnate summoning to transform into Chaos Bahamut . Sometimes when an Eidolon manifests its eidolith can be damaged ; this happened with Odin ' s eidolith when Odin manifested during Lightning ' s argument with Hope and the damaged part stayed in the Vile Peaks . When Caius caused paradox es along the timeline , a twisted manifestation of Odin appeared and attacked the Blitz Squadron . The party ' s eidoliths also appear as adornments for recruitable monsters . The party ' s eidoliths appear as gained from . " Mobius Final Fantasy " . Lightning ' s eidolith appears to her after Odin is defeated during the " Final Fantasy XIII " collaboration event .