Final Fantasy XII begins in Dalmasca's capital city of Rabanastre, where the happiness from the union of Princess Ashe of Dalmasca and Prince Rasler of Nabradia is interrupted by the Archadian Empire's invasion of Nabradia. In the subsequent war, Nabradia and Dalmasca are subjugated by Archadia; Prince Rasler is killed, and the Dalmascan king
Raminas, after signing a treaty of surrender, is apparently assassinated by the Dalmascan captain Basch. Reks, a young knight under Basch's command, bears witness to the assassination, but later dies of his injuries. Marquis Ondore announces that Basch has been executed and Princess Ashe has committed suicide.
Two years later, Vaan, the younger brother of Reks, is living as a street urchin in Rabanastre. Despite his friend Penelo's objections, he infiltrates the Rabanastre palace during a dinner celebrating the appointment of Vayne Solidor as consul. During the infiltration, Vaan encounters Balthier and Fran, a pair of sky pirates who are after the magicite that Vaan took from the royal treasury. Their escape attempt fails when a battle breaks out between Imperial troops and Dalmascan Resistance forces, and they end up in the sewers where they stumble upon the Resistance leader, Amalia. Vaan, Balthier, and Fran are captured by the Archadians and detained at the Nalbina Dungeons. In Nalbina, the three encounter Basch, imprisoned but alive, and they escape with him; Basch pleads that his twin brother, Gabranth, had posed as him on the night of the treaty and was the true assassin. While skeptical at first, Vaan eventually believes him. With the help of Balthier and Fran, the party then travels to Bhujerba, where Penelo is kidnapped by Ba'Gamnan, a bounty hunter trying to catch Balthier. While rescuing Penelo, the party meets Lamont, a curious boy who is Vayne's younger brother, Larsa, in disguise. Basch is also able to confront the Marquis, who captures the party and detains them on board the Archadian airship Leviathan, headed by Judge Ghis.
On the Leviathan, the party is reunited with Amalia, who is revealed to be Princess Ashe. Ghis takes Vaan's magicite, a royal Dalmascan artifact, and sends it to Archadia. The company escapes from the airship after defeating Ghis and returns to Bhujerba; however, lacking the magicite, Ashe has no proof of her identity and Ondore suggests that Ashe remain hidden in Bhujerba. Instead, Ashe escapes and attempts to collect the treasures of Dynast-King Raithwall, which would prove her royal blood. The party acquires the Dawn Shard, a piece of "deifacted Nethicite", from Raithwall's Tomb, but Ghis seizes it. The small piece of magicite destroys the Leviathan, Ghis, and his fleet, while Ashe and her party barely escape alive. The company later encounters Larsa, who seeks a peace treaty between Dalmasca and the empire; Ashe initially objects, but Larsa convinces her to pursue a treaty in order to protect Dalmasca. She goes to Mt. Bur-Omisace to seek Gran Kiltias Anastasis' approval of her as queen of Dalmasca.
The party learns in Mt. Bur-Omisace that many other influential people also hope to avert war. Larsa, who had been investigating Vayne's connection to the manufacted Nethicite, had made contact with Al-Cid Margrace, a member of the Rozarrian Empire ruling family, to convince the two Empires to cease their war. They plan to announce Ashe's status as Dalmascan Queen and to persuade the Archadian emperor Gramis not to go to war, but the plan is thwarted when the Emperor is killed, supposedly by Archadian Senate Chairman Gregoroth, and Vayne assumes the throne of Arcadia. With Anastasis' aid, Ashe retrieves the Sword of Kings, which can destroy Nethicite. While she obtains the sword, Anastasis is killed by Judge Bergan and Larsa is brought back to Archadia. After defeating Bergan, Ashe's party travels to Archades and the Draklor Laboratory, Doctor Cid's base of operations. Cid escapes and leaves clues that lead them to Giruvegan, the supposedlocation of the Sun-cryst, the source of all deifacted Nethicite. While the whole party is able to enter Giruvegan, only Ashe encounters the makers of the Sun-cryst, the immortal Occuria, who "pull the strings of history"; they give her the Treaty Blade to cut pieces of her own.
In a cutscene, it is revealed that Doctor Cid's Nethicite research was augmented by knowledge from the Occurian heretic, Venat, who had allied with Cid and Vayne in order to put the "reins of History back in the hands of Man". Vayne aims to become the new Dynast-King by using manufacted Nethicite to conquer all of Ivalice. Cid, revealed to be Balthier's father, was obsessed with researching the Nethicite's power after his own visit to Giruvegan and initial encounter with Venat. Their expansion campaign—which led to the Dalmasca's occupation and the destruction of the city of Nabudis—was made to obtain and study deifacted Nethicite.
Ashe is faced with the choice to heed the Occuria and take pieces of the Sun-cryst for her revenge or to destroy it and end the Occurian control over history. Still undecided, Ashe and the party travel to the Pharos at Ridorana Cataract, where the Sun-cryst is located, accompanied by the pirate Reddas. At the top of the tower they face Gabranth, who admits to killing King Raminas in an attempt to force Ashe to give in to her hate. After they overpower him, Cid arrives and fights the party; they defeat him, but before he dies he uses Nethicite shards to harness the full power of the Sun-cryst. Reddas sacrifices himself to destroy it.
Ashe learns from Al-Cid that a war between Archadia and the Resistance group led by Marquis Ondore is about to take place in Rabanastre. The Sky Fortress Bahamut, an enormous, Nethicite-fueled airship armed with incredibly powerful weapons, had absorbed the incredible amount of Mist released by the destruction of the Sun-cryst and now hovers above Rabanastre. Infiltrating the Bahamut with the aid of the Resistance, Basch confronts Gabranth, who is impressed by Basch's loyalty. The party encounters Vayne and Larsa in the midst of an argument over Vayne's plot for power, to which Larsa objects strongly; Larsa and Gabranth ally with the party to destroy Vayne and Venat. After Vayne's defeat, Ashe announces the end of the war, and Larsa takes over the Imperial Army. The party escapes the Bahamut, now out of fuel after the final battle, with Gabranth's body and Larsa. Balthier and Fran remain on board the Bahamut, steering it away from Rabanastre to prevent a collision, though contact with them is lost.
In the following year, Ashe becomes Queen of Dalmasca, and Basch replaces Gabranth as Judge Magister, serving as guardian to Larsa, now Emperor of Archadia. Vaan acquires his own airship, which he operates with Penelo. Balthier and Fran escape from Bahamut and survive to recover the Strahl and go to Bervenia. The game ends with Vaan and Penelo setting out to visit them, embarking on another adventure.
