Kings of Lucis

Kings of Lucis form the Lucis Caelum bloodline that wields the Crystal's powers by birthright in the Final Fantasy XV Universe. They are the monarchs of the kingdom of Lucis. According to legend, the Crystal is of divine origin and was bestowed to humanity alongside the Ring of the Lucii, which harnesses the Crystal's power for a chosen few.

Profile
When a king of Lucis dies, their spirit is taken by the Ring of the Lucii. The one who wears the ring can communicate with the spirits of the past kings, and the ring is what links the kings' spirits to the mortal realm. Although spirits that dwell in the "realm beyond" cannot usually influence the mortal realm, the past kings of Lucis are special in this regard, as the kings can combine their powers across generations in a phenomenon known as the bonding of the souls. The "bonding" can extend to those outside of the Lucian lineage at the king's behest, as shown in Kingsglaive: Final Fantasy XV where the Kingsglaive wield some of King Regis's magic, and in Final Fantasy XV where Prince Noctis's friends share in some of his powers, such as forging weapons from thin air and using magical potions and Elemancy.

The kings are entombed across Eos in hidden Royal Tombs, and leave behind Royal Arms to empower their descendants who seek them out. Only those of the Lucian lineage can brandish the Royal Arms, which glow when grasped by their rightful wielders. Using the Royal Arms drains the wielder's health, but they are especially good against beings of the dark, the antithesis to the Crystal and its light. The Lucian bloodline has a special power to brandish their inherited Royal Arms all at once, although this state can't usually be sustained for long. The weapons will materialize as crystalline silhouettes that circle the king who can rapidly attack their opponent with a new weapon each hit. The Royal Arms each have wing motifs upon them.

The Crystal is a magical stone said to be of divine origin that is a source of immense power. Though its light is said to be for the benefit of all of mankind, only the kings of Lucis have been gifted the ability to wield its power. In return, the kings are sworn to protect it. For the last 150 years, the king who protects the Crystal has shielded it from outsiders by maintaining the Wall, a magical barrier that isolates Lucis from the rest of the world. Upholding the Wall drains the king's life-force, accelerating their aging. Having conquered all other lands, bar Lucis behind its magic barrier, Niflheim Empire reigns supreme, only repelled by those who derive their power from the Crystal.

The Old Wall is a series of towering statues strewn throughout the crown city of Insomnia. Honoring the ancient kings of Lucis, who dwell within the Ring of the Lucii, it activates when the city is in danger at the behest of the current king if they are strong enough, or one deemed worthy by the kings of old.

Story
In the Old Calendar Era, the astral god Ifrit betrayed the rest of his kind and began the Great War of Old that killed millions. Ifrit sent forth the Starscourge, a plague upon the planet that lengthens the night and turns people into daemons. Ifrit is opposed by the other astrals who want to purge the darkness Ifrit brings forth by the powers of light, and thus Bahamut handpicked two people who would become able to wield divine powers to counteract the Starscourge, and to one day save the world from it. This became the prophecy of the True King.

According to legend, Bahamut picked the first Oracle from the land of Tenebrae. The Oracle's calling is to help the king of Lucis, and has the power to commune with the astrals and heal those afflicted with Starscourge. Bahamut also gifted the king of Lucis the Crystal alongside the Ring of the Lucii, so that one day the True King would be born of their lineage and banish Starscourge from the world. The Lucian kings are sworn to protect the Crystal until that day arrives, and gain the ability to use various magical abilities as facilitated by the Crystal. The Crystal exudes great magical power, and is said to hold the soul of the world.

The Lucian royalty can combine their powers across generations, as the one who wears the Ring of the Lucii can wield the powers of the kings of old. Thus, the power of the Crystal gradually concentrates until the king who wields all of the Crystal's power will be crowned the True King. The True King is said to surpass even the gods and have the power to banish the darkness from the world at the cost of his own life.

With the plan to cleanse the world of Starscourge in motion, Bahamut appears to have disappeared from Eos. Ardyn Lucis Caelum was a Lucian king chosen to save Eos from the Starscourge. He was revered for a time as he absorbed countless daemons to save thousands across the world, yet was denounced by the astrals as unclean. He was denied entry to the Astral Realm and demonized by a jealous future king (likely Ardyn's relative, as he also was of the Lucis Caelum royal bloodline) who later became chosen by the Crystal. As his transition rendered him immortal, Ardyn took the surname of "Izunia" and vowed to one day have his revenge on the Caelum dynasty and the Crystal.

Millennia pass, and the 113th king of Lucis is Regis Lucis Caelum CXIII. Though the Wall he upholds only now covers the crown city, his health is failing him at 50, and he only has one heir: the 20-year-old Prince Noctis. Regis ponders for how much longer he can keep projecting the Wall, but is reluctant to pass the torch onto his beloved son, knowing it would in time do the same to him. As implied in the Omen short film, Regis knows Noctis will be the Chosen King spoken of in legend, as he learns the Crystal only needs one more life: his own. Regis thus decides to accept a suspicious peace treaty with Niflheim, with whom Lucis has warred for hundreds of years. Regis sends Noctis away from the city before the signing is to take place to keep him safe and to give him the best chance of fulfilling the prophecy.

During the treaty-signing Niflheim forces draw their weapons upon the Lucians and war breaks out amid the crown city. Emperor Iedolas Aldercapt and Ardyn—who has established himself as the chancellor of Niflheim—steal the Crystal and the Wall dissipates. The crown city is invaded by daemons and magitek troops. General Glauca is tasked with taking the Ring of the Lucii from the king, and it is also sought by Ravus Nox Fleuret, the former prince of Tenebrae who is of the Oracles' bloodline. Ravus begrudges Regis and his kingdom for having abandoned Tenebrae when Niflheim invaded it, and believes his heritage entitles him to the ring's powers and could make him the True King. When he acquires the ring and puts it on however, he is judged unworthy by the past kings and the ring burns him, although he survives with a lost limb.

Regis is accompanied by Lunafreya Nox Fleuret, the Oracle and Ravus's sister who has never blamed Regis for Tenebrae's downfall and is Prince Noctis's childhood friend, knowing her calling is to help him become the Chosen King. They are protected by a member of the Kingsglaive, an elite unit of soldiers for whom Regis has lent the ability to use his magic: Nyx Ulric. Regis passes on the Ring of the Lucii to Luna with instructions to take it to Noctis. He stays behind to fight Glauca to give Luna and Nyx time to escape, and is killed, his spirit entering the ring.

Nyx is soon attacked by one of his fellow Glaives who has turned against the monarchy, Luche Lazarus. Luche he is tricked into putting on the ring and is deemed unworthy by the past kings and burned alive. Nyx's superior, Titus Drautos, reveals himself to be Glauca, and attempts to claim the ring. Nyx puts it on and finds himself in another dimension, where he speaks to the deceased Lucian kings and faces their judgment.

When the kings see Nyx fights for the future, at the spirit of King Regis's urging, they grant him their power in exchange for his life. Nyx passes the ring to Luna, then uses the Ring of the Lucii's power to engage Glauca. The resulting battle sees Glauca fatally stabbed by Nyx, with the Empire's daemons destroyed by the Old Wall, summoned effigies of the past kings of Lucis. Nyx dies at dawn as part of the blood price of using the ring's powers.

Luna escapes Insomnia with the Ring of the Lucii and eventually makes her way to Altissia where she speaks with her brother Ravus. She asks him to take the ring to Noctis as she is collapsing from the strain of her duties, but he turns away at the sight of it, and says delivering the ring to the Chosen King is her duty. Although Ravus doesn't think Noctis is worthy of Luna's sacrifice, he has come to believe the prince is the only one who can become the True King.

Noctis is on a journey to collect the Royal Arms of his forebears and forge covenants with the astrals with faraway help from Luna. He believes his mission is to reclaim his kingdom by toppling the Empire, and is initially unaware of his role as the True King. He is being helped by Ardyn Izunia, although Noctis doesn't like or trust him. Though chancellor of Niflheim, Ardyn is actually Noctis's immortal ancestor and an embodiment of darkness and the Starscourge as his soul has been corrupted by daemonic influence. Ardyn is thus also a Lucian king, but one fallen from the gods' and the Crystal's favor and his name has been scrubbed from history books. He seeks to extinguish the Lucian bloodline as revenge, and defeat the True King. Knowing that this is Noctis's fate, Ardyn helps the prince get the full powers of the Crystal so that he could then destroy him.

Luna calls upon the souls of Lucian kings when Noctis fights the astral Leviathan to forge a covenant with her. The kings answer, the Royal Tombs across the land light up, and Noctis enters a sustained mode of Armiger, the power of kings that lets him wield all of his Royal Arms simultaneously. Noctis receives the Ring of the Lucii from a dying Luna, and eventually makes his way to the imperial capital where the Crystal now lies. His mission has shifted from just reclaiming Lucis to that of saving the world, as without Luna keeping the darkness of the Starscourge at bay, daylight is rapidly vanishing from the world. Noctis believes he can use the Crystal's power of light to fight the darkness, but when he finds the Crystal he is absorbed inside it. He meets Bahamut and learns he must sacrifice his life to bring light back to the world. Noctis sleeps inside the heart of the Crystal for ten years, during which Eos is plunged into an eternal night and daemons take over the world. People's only hope is that the fabled King of Light of the Lucian lineage will come as per the prophecy.

Noctis returns ten years later and confronts Ardyn in the ruins of Insomnia to where the former has taken the Crystal. Ardyn ushers Ifrit upon Noctis, but he prevails with the help of the other astrals. Noctis battles Ardyn both wielding the power of kings, but Noctis emerges victorious and ultimately kills Ardyn by drawing his Royal Arms and striking him with each one.

He calls upon the spirits of past Lucian kings to be able to confront Ardyn's spirit in the afterlife. The spirits of the old kings attack Noctis until his soul is taken by the ring, and his spirit enters a realm of full of light similar to the place inside the Crystal where he had met Bahamut. Noctis uses the power of light to banish darkness from the world and erase Ardyn's soul. The prophecy fulfilled, the Ring of the Lucii disintegrates as the Lucian bloodline ends with Noctis's death. His spirit appears upon the throne of Lucis marked Noctis Lucis Caelum CXIV with Lunafreya Nox Fleuret, the last Oracle.

Trivia

 * There being thirteen past kings who aid Noctis in his final struggle, as well as thirteen Royal Arms, is an allusion to number thirteen, as per the game's origins as Final Fantasy Versus XIII.
 * The Lucian kings could also be compared to l'Cie from the Fabula Nova Crystallis: Final Fantasy series to which Final Fantasy Versus XIII was part of, as they have a mission to a Crystal. "Lucis" and "l'Cie" sound similar, although this could be a coincidence. Both the Lucian kings from Final Fantasy XV and l'Cie from Fabula Nova Crystallis are also homage to Warriors of Light, the traditional Final Fantasy heroes who answer the calling of a crystal.
 * Lucis had a more overt relationship to the Grim Reaper in earlier drafts, but this was toned down due to ratings concerns. Imagery relating to skulls still appears among the main cast's outfits and the insignia of Lucis. This may allude to the revering of the dead kings.
 * The spirits of the past kings allude to the Knights of the Round, a recurring summon in the Final Fantasy series. The thirteen Lucian kings of old appear during the final encounter, similar to how the Knights of the Round perform when summoned in Final Fantasy VII.