Heart of Chaos

The Heart of Chaos is a manifestation of the goddess Etro, and it is her own heart. It resides within the chest of Caius Ballad.

Datalog
''The Heart of Chaos is the goddess Etro's own heart, given to Caius. It is the font of the immortal Guardian's power. Only if another potential Guardian defeats him and takes this power can Caius truly be killed. And the only person remaining in this world with that potential is Noel.''

''If the new Guardian has enough strength of will, he can release the Heart's power and put an end to immortal destiny. If he wavers, however, he will be enslaved in chains of chaos, and become the latest in a line of eternal servants.''

Story
During a time before the War of Transgression, Etro recognized the l'Cie and Guardian Caius. She saw his dedication to protect the seeress Yeul and took pity on him. Etro released Caius from his fate as a l'Cie, and 'blessed' him with the Heart of Chaos, thus granting him immortality, and enabling him to protect Yeul's reincarnations throughout time. Etro's act however would been seen as a curse of eternity to Caius, dooming him to bear the sight of hundreds of Yeuls dying before his eyes. Driven mad, Caius waits centuries for the right person who will be able to pierce the Heart of Chaos, therefore killing Etro and freeing him from his curse.

The only person capable of freeing Caius is Noel Kreiss, a young hunter born in a Dying World around the year 700 AF. Caius takes Noel under his wing and trains him to become a Guardian to Yeul like himself. When Noel shows the right potential, Caius challenges the unwilling boy to battle, hoping that Noel will release him. The duel ends with Caius winning however, causing him to resolve to kill Etro himself in Valhalla. Caius does not succeed in this as the goddess is protected by her champion, Lightning.