There are two planet spheres. Cocoon and Pulse. Most of the gang is all from Cocoon. Cocoon is a modern society where life basic necessarities are provided by these God-like structures called "Fal'cie". The other planet, the planet down below is Gran Pulse. The people of Cocoon believe that Pulse is wild and uncivilized. No one lives there. Pulse also has the giant god like Falcie. Cocoon an Pulse Falcie are at war with each other. In order for each to make an army, the Falcie from each planet turn humans into l'cie. People with super strength and magic. So, you get cocoon l'cie "those turned by cocoon Falcie" and pulse l'cie "those turned by pulse Falcie"

In the begining of te game, the party was fighting on Cocoon. But there lay a Pulse Falcie on Cocoon! Dun dun dun. The pulse Falcie, Anima, turned the party into Pulse l'cie. Meaning, an Enemy of cocoon. L'cie are given a mission, a focus, to complete for the Falcie. If they don't hurry up and do it, they turn into a zombie, cieth.

Why are people being "purged?" The people of cocoon live pleasant lives. They are fearful of the planet down below, pulse. So when they hear that a pulse falcie had managed to get onto cocoon and turn them into Pulse warriors, the people panic and demand anyone in contact to be sent to Pulse. The gov, the sanctum , listened to the people and was forcefully relocating everyone who was near the town of Bodhum to the planet Pulse. Where they would likely die. Snow and others fought against this genocide, and that's what the battle taking place is. The party hops on board to that big ship in order to rescue Sazh and Vanille. Who are going to be publicly executed. This is being done to keep the people feeling safe. "Don't worry people, we are going to kill the pulse l'cie. We have it all in control."

So, they decide to go after those in the gov that are leading this genocide.

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