Noctis and his three friends begin their journey to Altissia, the capital of Accordo, where Noctis's wedding to Lunafreya will take place. Finding the local boat services stopped, they receive news of Niflheim's attack on the city of Insomnia and theft of the Crystal; King Regis has been assassinated, and both Noctis and Lunafreya are declared dead. Meeting up with Cor, Noctis is tasked with retrieving the Royal Arms—the magical weapons of past Lucian kings—to rescue the Crystal and reclaim his throne. While staying in the city of Lestallum with Iris, Noctis is contacted by the Astral Titan; encouraged by Ardyn Izunia, Noctis endures Titan's trial and earns his power, learning that Lunafreya is traveling ahead of Noctis to awaken the Astrals from their slumber. The group continues to travel across Lucis, retrieving the Royal Arms and meeting the Astral Ramuh with assistance from Gentiana, Lunafreya's spirit attendant, in addition to confronting a hostile Ravus, sparring with the mercenary Aranea and receiving further aid from Ardyn. They also recover parts to repair Regis's old yacht, using it to travel to Altissia.

The party arrives in Altissia, where Lunafreya has taken sanctuary. Lunafreya awakens the Astral Leviathan so Noctis can obtain her power, only for Leviathan to go on a rampage when Niflheim attacks. Ardyn then appears and mortally wounds Lunafreya, disrupting the ritual; however, she succeeds in awakening Noctis's powers, allowing him to defeat Leviathan. While unconscious, he is visited in a dream by Lunafreya's spirit, who gives him the Ring of the Lucii. Noctis wakes to find Altissia in chaos, and that Ignis was blinded during the battle. The party continues towards Niflheim's capital of Gralea by train, while Ignis' blindness and Noctis's mourning of Lunafreya cause friction between Noctis and Gladiolus until Ignis forces a reconciliation. It is also revealed that the nights are growing longer, causing more Daemon attacks. Ardyn then tricks Noctis into throwing Prompto from the train, and holds Prompto and the Crystal captive in Gralea's main fortress, revealing the Crystal's power can destroy the Daemons. Noctis continues to Tenebrae, where Aranea is aiding refugees from across Eos. While in Tenebrae, Noctis learns that Lunafreya was dying from waking the Astrals, and that Ravus now supports him. On the final journey to Gralea, the train is ambushed by Daemons; after defeating them, Noctis receives the Astral Shiva's blessing from Gentiana, who reveals herself to be Shiva's human form.

Arriving to find Gralea overrun by Daemons, Noctis is separated from his friends and forced to use the Ring of the Lucii to survive Zegnautus Keep, Niflheim's military center. After reuniting with and rescuing Prompto, the party continues through Zegnautus Keep, defeating Ravus and Emperor Aldercapt, who have been transformed into Daemons. Forced to leave his friends behind, Noctis finally reaches the Crystal, only to be pulled into it. Ardyn appears and reveals himself to be Ardyn Lucis Caelum, a former healer whose infection by the Starscourge led to the Astrals and Crystal rejecting him; rendered immortal by the Starscourge, Ardyn has since sought revenge on the royal bloodline and the Crystal, hastening the onset of the Starscourge while waiting for the True King to appear so he could destroy them both. Within the Crystal, Noctis encounters the Astral Bahamut; he learns that he is the True King of prophecy, who will cleanse the Starscourge and restore light to Eos at the cost of his life. Noctis returns to Eos after ten years, finding the world engulfed in darkness. Reuniting with his friends, Noctis heads for Insomnia, fighting the rogue Astral Ifrit before facing Ardyn. After killing Ardyn in single combat, Noctis ascends the throne and sacrifices himself, using the power of the Lucii—including the spirit of Regis—and the Crystal to purge the Starscourge from Eos. In the afterlife, with help from Lunafreya and the Lucii, Noctis destroys Ardyn's spirit. In mid-credits and post-credits scenes, Noctis opens up to his companions before the final battle, and finds rest with Lunafreya in the afterlife.

The narrative is expanded with later downloadable content (DLC). In Episode Gladiolus, Gladiolus leaves the group to test his strength against recurring Final Fantasy character Gilgamesh following the group's first confrontation with Ravus.Episode Prompto takes place after Ardyn tricks Noctis into throwing him from the train to Tenebrae, and focuses on Prompto's past as the vessel for one of Niflheim's Magitek soldiers. With help from Aranea, Prompto defeats Verstael—who transfers his soul to the Magitek creation Immortalis to conquer Eos—before heading for Gralea. In Episode Ignis, Ignis allies with a disillusioned Ravus in the wake of Leviathan's rampage. After finding Lunafreya dead and Noctis unconscious, they are ambushed by Ardyn; Ignis uses the Ring of the Lucii to fend him off, which costs him his sight. In the story mode for the multiplayer expansion Comrades, the player controls a survivor of the Kingsglaive, Regis's bodyguard who betrayed him during Niflheim's attack. Despite the people's mistrust, the Kingsglaive help defend humanity's last stronghold of Lestallum while experiencing visions of Noctis' resting place on the island of Angelgard. Drawn to Angelgard, the Kingsglaive face Bahamut in combat and are absolved of their treachery, dedicating themselves to protecting Angelgard from Daemons during Noctis's slumber

Gameplay