Final Fantasy XIII: Crystal Reverbations is a game taking place about one year after Final Fantasy XIII, focusing on the old group of l'Cie (minus Fang and Vanille), and a squad of newcomers. The game, unlike other Final Fantasies, is a mix between the ATB and third-person shooting, where movement and firing don't waste ATB bars, but special abilities do, determined by the four new Paradigms.
Note: This is only a recapping of the main plot. Side mission plots don't count.
In a short video, the events of Final Fantasy XIII are recapped. Lightning is finally showing some emotion, mostly because of Serah's return, and that PSICOM is still resisting, but is attempting to take over Cocoon through hostile measures. The l'Cie are the main guardians of Cocoon, though Team NORA is still fighting strong in other areas.
The game opens with Lightning looking at a stone which reads "DEDICATED TO ALL WHO DIED IN THE PURGE". As Lightning wonders if there are any survivors, the tutorial takes the player to a squad of four men: Warchief, the leader; Sledgehammer, the brawns and engineer; Scalpel, recon and medic, and Necksnapper: team sniper and stealth soldier. Together, they make up the prestigeous and experimental Honor Squad. Dropping into the area, they use grav-cons to slow down and touch down on the battlefield. After a short walk, it is revealed they are not there for a spec ops operation: they are to take part in a Purge. Upon discovering their true purpose there, they split off from PSICOM, rescue a few people, and then face a scorpion robot. Despite their best fighting skills, the war is futile, and Honor Squad is incapacitated before the Pulse train falls and their bodies hit the ground.
One year later, Warchief wakes up on a hospital bed in Bodhum. The world has apparently changed, and he gets up. Wearing the clothes he did when he was incapacitated, he finds his armor in the room and puts it on. With everything active, he leaves the hospital. As soon as he does, the computer built into his armor recieves a message from someone known as "Odin", saying that Warchief can meet the people that recovered his body at that point. Odin has also provided him a bed. Warchief begins the walk: after a few minutes of hopping fences, jumping onto buildings, and crossing rooftops to refresh his abilities (and serve as a tutorial to advanced movement), he eventually arrives at the area, which is a house. Sliding down the drainage pipe, he knocks on the door, to meet Snow. Snow takes him in, shows him around, and says the rest of his squad is here.
Heading into the guest room, Warchief gets a brief reunion with the rest of Honor Squad, before falling to sleep. He then wakes up to an attacker, who came for Fang but didn't realize she isn't here. Bringing buddies, they are too easy to defeat, and Honor Squad takes up the room. Warchief moves out and, to the shock of everyone realizing they're harboring experimental soldiers, neutralizes all targets before Lightning decapitates the last one. After formal introductions, they settle into a routine. Later in the day, Scalpel takes a message saying that they're looking for Lightning at the mall, and will head to the house if he can't find her. Scalpel informs him, and Warchief volunteers to go with Lightning.
At the mall, sensing the target is close, Warchief ducks into a washroom and activates a cloaking system (the game teaches the character about the Paradigm Shift move at this point, which simply allows you to switch roles and powers). Staying close to Lightning, the two pass a shady person. In the parking lot, the character tackles Lightning, only to be met with a carbine shoved into his face from Warchief. Warchief bluffs that he would shoot the man would the situation require it: the man decides to call his bluff by puncihg Lightning in the face. He is then shot in the shoulder, which Warchief says is a "warning shot". Making sure nobody else is there, Warchief lets Lightning punch the man in the face before they leave.
A few months later, everyone has made fast friends. Scalpel has made good friends with Hope, which started after he dissected Warchief's shoulder-mounted rocket launcher and then put it back together - in full working order. Necksnapper is teaching Serah sneaking and self-defense, to the point that when she shows off, instead of mock breaking his arm, Serah literally full force breaks Necksnapper's arm and then punches him in the face. Necksnapper simply hobbles off stating it as an "occupational hazard", and becomes friends with Serah because of that. Sledgehammer taught Sazh how to use the exoskeleton: saying that he may need it in the future. Finally, Warchief has surprisingly bonded with Lightning (which Snow responds as "Against all odds"; the rest of Honor Squad, and the group, agrees). Warchief begins fighting for the Guardian Corps for the future of Cocoon, taking three operations before death threats start coming in to the group from an un-noticed reformed PSICOM. Scalpel hurries to finish the first suit of new armor, which Hope tries: he finishes the assault course flawlessly.
The Guardian Corps eventually hire Honor Squad, and finish the armor for the rest of the makeshift family. Lightning is one day attacked: she figures out it's a PSICOM assassin, and that there are more. Sending out a distress signal, Honor Squad arrives within minutes, to find Lightning gone: a victim of abduction. Distress signals then overflow Honor Squad's capacitors: Snow, Hope, Serah, and then Sazh send distress calls. Honor Squad decides to split up. Warchief goes after Sazh, Scalpel goes after Hope, Serah becomes Sledgehammer's target, and Snow is to be rescued by Necksnapper. Warchief fails: his straightforward assault strategy isn't enough to match the assassins, who knock him out and get away with Sazh. Scalpel almost saves hope, but is then fired on by a sniper: using his exoskeleton, he manages to dodge the shots, only for an unseeen assassin to crack him across the back of his head. Scalpel is knocked out and Hope is taken. Sledgehammer manages to silently take out every last one of Serah's attackers: he is the only one to succeed. Finally, Necksnapper attempts to sift Snow's attackers, but fails.
After Sledge, Serah, and Neck wake up the rest of Honor Squad, Sazh, Snow, and Hope team up to battle their way out of the enemy's clutches. Hope attempts to rescue Lightning, but is stopped by Sazh, who calmly says "Let Honor Squad do it". Making their way out of the base, Honor Squad and Serah grab everyone. Serah and Snow share a teary reunion, interuptted by Warchief, who yells, "We have time to cry over each other when we're not being shot at!" Warchief leaves, and Honor Squad begins formulating a plan to rescue Lightning.
Getting the whole of Guardian Corps on their side, Honor Squad raids several PSICOM outposts before the final assault on the PSICOM base. Fighting through elite soldiers, they reach Lightning, who is being held by a no-longer-Fal'Cie Eden. After a long battle, where an explanation is set up (because of the loss of Odin, Eden lost his god status), Eden uses the now-awake Lightning as collateral to ensure that he survives: knowing Lightning will probably die either way, Warchief steps up. Relenting for a second, as Eden drops his human shield, Warchief calmly and quickly raises his pistol and kills Eden.
Yet another year later, everyone has moved to a larger house on the edge of Bodhum. Lightning and Warchief play the recently-released game Super Street Fighter IV: Lightning masters Juri near-instantly, and builds up her Super meter. Letting Warchief hit her, Lightning then uses her Ultra Combo II, eliminating Warchief (who is playing as Ryu). Hope is still playing around with his suit, but the rocket launcher is yanked off by Scalpel after he destroys a tree in three places when he unknowingly uses it. The game cuts to display a look at Pulse: with a monologue by a disembodied voice. "They are not alone, and they never will be. First contact happens now."
The gameplay is similar to a revamped Final Fantasy XIII battle system. Warchief moves around, usually with his squad, as a group: he can order the squad to attack targets. Movement and firing (which are substantially faster) do not waste ATB segments: special actions performable by each Paradigm do. Each of the four Paradigms: Assault, Engineer, Scout, and Sniper, have different abilities: Assaults can use a grenade launcher/shotgun and a rocket launcher that drains all of the ATB segments but deals massive damage, for example. Engineers can use a set of robotic leg braces, called an Exoskeleton, to move substantially faster: the ATB is drained depending on sprint length. Engineer can also waste his entire ATB bar to call in an airstrike from a UAV, and can also summon a robotic drone which carries a chaingun. Scout can detect enemies earlier and most likely fires the first shot, and Sniper can cloak and silently dispatch enemies with no need for a fight. Each Paradigm can only use one ability.