Is this information about Caius revealed/hinted during the game?

Question

Recently, I was directed to this Wikia page about Caius Ballad: http://finalfantasy.wikia.com/wiki/Caius_Ballad#Story

Some of the info there was clearly presented in the game. But there are some rather detailed things that I don't remember ever seeing in the game. Perhaps these details are indeed hinted during the game, so I will point some out from that page:

• The fact that Caius once fought against a very powerful warrior of the Farseers, who then sacrificed himself at the arrival of an enemy army to save Yeul and then Caius took his last name 'Ballad'
• "To protect Yeul himself, Caius performed an incarnate summon to destroy the enemy forces" - I mean, we do know he can transform into bahamut, but I don't remember anyone ever mentioning an "incarnate summon" spell performed by Caius or anything.

So, are those facts hinted somewhere at all in the game, or is there an external source about this? Where?

Answer 1

The details of Caius's backstory are described in the fragments.

The first fact is described in the Helmwige's Nightshade fragment:

Caius, the peerless hero celebrated in Paddra legend, was a Guardian, appointed to serve and protect the seeress. The sages sung of his countless victories, of foes vanquished in the thousands. He was called 'Caius of the Ballads,' but despite his renown, none knew his true origin.

He took the name 'Ballad' because of the one battle that nearly killed him.

The foe was a fellow warrior of the Farseers. Overwhelmed by the strength and skill of his opponent, Caius was driven back and back, until it was only a matter of time before the final blow would fall. But their duel was interrupted by an enemy attack, and during the ensuing battle Caius's opponent gave his life defending the seeress. Caius believed that it was he who should have fallen in her defense. Thus, to honor the fallen warrior, he took his name.

The second is described in the Chaos Brand fragment:

A massive battle once raged on Gran Pulse. Paddra was beseiged by a great army that sought the life of the seeress. In the face of their assault, Caius chose to perform an 'incarnate summoning.' This ritual merged his essence with that of the Eidolon Bahamut, and drew forth all their latent power.