Beginning in one of Eorzea's three main states, the player character awakens to the Echo, a power granting them the ability to see the past.[3] The Adventurers are initially involved in both conflicts within the nations provoked by the Garlean presence, led by the Garlean Legatus Gaius van Baelsar, and the beastmen's attempts to hoard crystals and summon their primals. Eventually, a greater threat is brought to the attention of the nations by the Sharlayan scholar Louisoix Leveilleur: another Garlean Legatus named Nael van Darnus is using arcane magic and technology to summon Dalamud, the planet's second moon, down on Eorzea to purge the beastmen and primals whom the Garleans hate as violent pagans. With the aid of Garlean defector Cid nan Garlond, the Adventurers discover that Nael has set up a beacon for summoning Dalamud in the new fortress of Castrum Novum. While each nation makes individual attempts to storm the fortress, they are repelled. Faced with this, their leaders form a pact and unite the nations under the banner of the Eorzean Alliance.[10]
Now united, the nations, aided by Adventurers, successfully storm Castrum Novum and destroy the beacon. Nael, insanely committed to her plan, makes herself into a second beacon. Though she is defeated by the Adventurers, Dalamud has descended too far for it to return into orbit, so Louisoix proposes a final desperate plan: to summon the Twelve, Eorzea's guardian deities, and return Dalamud into orbit. The Adventurers pray to altars dedicated to the Twelve across the land, then rally with the armies of the Eorzean Alliance to fight Nael's legion on the Carteneau Flats, the predicted impact site of Dalamud. In the midst of the battle, Dalamud disintegrates and reveals itself to have been a prison for the elder primal Bahamut. Enraged after his imprisonment, Bahamut begins laying waste to Eorzea. After the attempt to summon the Twelve fails, Louisoix uses the last of his power to send the Adventurers into a time rift, separating them from the flow of time so they can return when Eorzea has recovered.[10]