We were both Guardians. Warriors who are charged with protecting the seeress.
In Final Fantasy XIII-2, Guardian is the title bestowed upon a warrior from a Farseer tribe tasked with protecting the seeress Paddra Nsu-Yeul from harm, given the mark of a l'Cie to ensure no failure. There can only be one Guardian any one time, and every warrior who shows potential must kill the present Guardian to succeed him. The last guardian is Caius Ballad, made immortal by the Goddess Etro and gaining a new objective in his role by remembering Yeul's visions, thus retaining memory of all timeline events.
The warriors who accompany and protect the seeress Yeul are chosen from among the most capable of the Farseer people.
A Guardian is the strongest of these, a defender that wields the power of chaos. This power is said to surpass even the godlike might of the fal'Cie.
Only one true Guardian is permitted to exist at any one time. Another protector of the Farseer tribe who challenges and defeats the champion becomes the new Guardian and wielder of chaotic energy.
The Heart of Chaos does not grant the Guardian power—it eats away at their physical self. Caius did not gain an immortal body, but was cursed with eternal life.
Heed my words, Noel. You are the last protector, and the only one who can wrest the Heart's strength from Caius. In the instant you strike the life from his body, you shall either inherit the curse, or break its eternal grip. Only your will can slay fate one way or the other.
One notable Guardian was Gorgyra, a girl who chose to become Yeul's guardian. She was once fooled and in turn the seeress's life was put in danger. Although Yeul forgave her Guardian, Gorgyra was not able to forgive herself and requested to become a Cie'th as punishment.
Caius was made a l'Cie tasked with the Focus of protecting Yeul after killing his predecessor. When her life was threatened by an army invading Paddra, Caius risked his own life to protect her by performing an incarnate summoning, where he fused with his Eidolon, Bahamut.
Doing so cost Caius his life, but the goddess Etro saw Caius's dedication to Yeul and took pity on him. She freed him from his l'Cie fate and gave him her own heart, the Heart of Chaos, thus making him Yeul's immortal Guardian. This act would become a curse of eternity that would cause Caius to descend into madness through the centuries that follow. He would continue to protect hundreds of incarnations of Yeul and remember their visions of the future, waiting for the day someone strong enough would surpass him and release him from the curse.
At the end of days in the Dying World in the year 700 AF, Caius's prayers were answered with the birth of Noel Kreiss. He becomes Noel's mentor and close friend while training him for the day the boy would be strong enough to defeat him. When that day comes, Noel does not wish to kill Caius but instead serve as Yeul's Guardian alongside him. Caius engages Noel in battle and emerges the victor much to his dismay. He abandons Noel and Yeul, seeking to free the latter from her curse as a seeress by going to Valhalla, the middle world betwee life and death, and killing Etro.
After the goddess opens her gate to Noel and sends him to Valhalla, he meets Lightning, Etro's protector, who sends him back into the past to find her sister Serah. She and Noel begin their journey through time together and learn she can also see into the future like Yeul, thus in a way granting Noel's wish by making him Serah's Guardian.
In a paradox ending Noel inherits Caius's Heart of Chaos and succeeds him as Guardian.
- The term, "Guardian" was first coined in the series in Final Fantasy X, where guardians were charged with protecting their summoners, and were used as the fayth for the final summoning. However, the role of a Guardian in Final Fantasy XIII-2 is more like the role of a Sorceress Knight from Final Fantasy VIII, who is charged with the protection of a sorceress, and in both games, only one protector can be assigned, as opposed to Final Fantasy X, where a summoner can take as many guardians as he or she wishes.