Caius Ballad is a boss in Lightning Returns: Final Fantasy XIII. He is fought at the end of the Temple of the Goddess, and unlike the other main quest bosses, doesn't become more powerful if fought on a later date.
Caius switches between two roles: Commando and Ravager. In Commando mode, Caius will predominantly use physical attacks, and while in Ravager mode, he will use magical attacks. His stagger bar is more effectively built using physical attacks while he is in Commando mode, and vice versa for magical attacks when he is in Ravager mode. Caius can be staggered up to four times, and gains a resistance to the element that staggered him.
Caius enters Commando mode at the beginning of the battle. Every time he switches to Commando mode, he opens with a Megaflare. Thereafter, Caius uses a combination of 1 or 3 Blast Waves, 2–5 hit sword combos (which may or may not include a knockback or a rising slash), 2–4 Gravitons in a row, a Giga-Graviton, a Pulsar Burst, and an Eye of Bahamut attack. The amount of abilities he uses in a single combo varies and depends on his health; the lower he is, the more attacks he will unleash.
After a while, Caius will switch to his Ravager mode, during which he will use "Readying", then "Gathering Energy", then finally "Ready!" in preparation of his strongest magic combo consisting of Flare, Chill, Surge and Tornado. Caius will use at least 3 to all 4 of them in a random order. Afterwards, he returns into Commando mode.
Before each stage of preparation (Readying/Gathering Energy/Ready!), Caius will unleash a combination of magical attacks, consisting of Flamesparka, Frostburna, Icestorma, Thunderstorma, Firaga, Blizzaga, Thundaga, Aeroga and Inferno. These combinations consist of at least 2–4 magical attacks depending on his health. Rarely will he continue to use Eye of Bahamut in Ravager mode. The lower his health is, the faster he will go through his preparation stages, sometimes skipping his regular magic combos to go straight into his strongest magic combo.
In either role, he can cast Absolution to remove current debuffs while placing buffs on himself: Body and Soul to buff himself plus regaining some health, and Invigorate to refresh the stagger bar on himself.
Early in the battle Caius's attacks will be slow and easy to anticipate, but once his health drops below 66%, he will start using abilities more frequently and cast status changes, either weakening Lightning, or strengthening himself. At 33% of his health, he will regularly heal himself and his attacks come out even faster. One of the enhancements Caius will cast on himself is Veil, and after casting this he will be virtually immune to debilitation abilities.
Sacred Knight is a powerful defensive garb that strengthens any forms of guard and comes with defensive strikes that allow Lightning to guard while striking. To acquire this garb, players must complete The Grail of Valhalla quest. A solid alternative for a defensive garb would be Paladin or Dragoon.
The garb Amazon Warrior is a strong physical attacking garb. It comes with Speed Slash and a normal Guard, but should not be used to defend from Caius's chain of attacks. However, if Sacred Knight or Paladin is still recovering ATB, Amazon Warrior's Guard is better than no Guard at all. Some alternative physical attacker garbs include Soldier of Peace, Rhapsody in Rose, Splendid Admiral, Velvet Bouncer, Dragon's Blood, and Innocence. Midnight Mauve is a solid choice for dealing magic damage. Fira is a powerful spell that can help quickly stagger Caius while he's in Ravager mode. Other potential useful garbs for magically attacking are Witching Hour, Intruder, Loyal Servant, and Black Mage.
Guarding is a must in this battle. Lightning's health can drop quickly if she isn't careful. When Caius begins to chain several attacks, Lightning must be guarding by then, otherwise, if Caius lands any blows, it will be too late to defend, and she will have to wait until the end of his attacks while receiving massive damage.
When dealing with Megaflare it is important to be in a defensive garb and attempt to perfectly guard against the attack. Too soon will result in heavy damage, while too late will result in either massive damage or Lightning crumbling in one hit.
While Caius is in Commando mode, one should focus on using physical attacks, and while he's in Ravager mode, players should focus on magic attacks. Periodically the player should switch into their defensive garb and defend against Caius's attacks, and then switch back into an offensive garb as soon as Caius has finished.
One should use debilitation abilities when Caius doesn't have Veil up, and take advantage of any of the garbs' special abilities, such as Transformation Protect from Innocence. If Caius is staggered at any time during combat, one should send Lightning into Overclock and unleash a barrage of devastating attacks.