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Description
Nyx Ulric hails from Galahd, a territory conquered by Niflheim's imperial forces. The invasion claimed his sister Arabella, but King Regis intervened to save Nyx, instilling a profound debt. This loyalty drove Nyx to join the Kingsglaive, an elite unit of immigrants empowered by Regis's magic. His exceptional combat skills and unique affinity for the king's magic earned him the "hero" moniker among peers. His childhood friend Libertus Ostium accompanied him to Insomnia and also enlisted.

Nyx possesses dark gray hair and blue eyes, adorned with subtle tattoos: a "crow's foot" on his right cheek, markings under his left eye and on his ears, lines descending his neck and fingers, and patterns on his back and limbs. He customizes his Kingsglaive uniform with a silver antler or horn on the hood, purple ribbons, and blue-gray fur pelts on his left sleeve, symbols of his Galahd heritage and hunter lineage. His twin kukris—one forged in Galahd, the other in Insomnia—represent his dual homelands.

Personality-wise, Nyx embodies selflessness and fierce loyalty, motivated by guilt over failing to save his sister. This trauma triggers flashbacks during combat, fueling his drive to protect comrades. While confident in battle, his resolve borders on arrogance, noted by Lucian kings during power bargains. He remains steadfastly loyal to Regis and Lucis, even as fellow Glaives betray the crown. His dedication extends to prioritizing friends like Libertus and Lunafreya during Insomnia's fall.

Nyx's combat prowess relies on warping via his kukris and wielding elemental magic like fire and lightning, abilities temporarily "on loan" from Regis. During the Niflheim peace treaty crisis, he disobeys orders to rescue Libertus from a daemon, resulting in disciplinary guard duty. After discovering fellow Glaive Crowe Altius's death, he confronts Libertus, who subsequently deserts. At the treaty-signing celebration, Nyx meets Princess Lunafreya and gives her Crowe's hairpin.

When Niflheim betrays Lucis, Nyx leads the mission to rescue the kidnapped Lunafreya, facing betrayal from most Glaives. He escapes with her and aids the wounded Regis against General Glauca, who severs Regis's hand to steal the Ring of the Lucii. Entrusted by the dying Regis with Lunafreya and the ring, Nyx flees while the king holds off Glauca. Pursued in Insomnia and cornered by traitorous Glaives, Nyx discovers their commander, Titus Drautos, is Glauca. To protect Lunafreya and Libertus, Nyx dons the Ring of the Lucii.

The ring's spirits reject Nyx for his non-royal blood and perceived arrogance. He convinces them by offering his life in exchange for power, arguing the ring's loss would doom Lucis. Granted control over the Old Wall—stone statues of past kings—he battles Glauca across Insomnia. After mortally wounding Glauca, Nyx returns the ring to Lunafreya for delivery to Prince Noctis. As dawn breaks, he succumbs to the ring's life-cost, his body turning to ash while wishing Noctis a prosperous reign.

Posthumously, Libertus maintains hope of reuniting with Nyx and leads surviving Glaives protecting Lucis during Noctis's absence. A decade later, Ardyn Izunia hangs an illusory version of Nyx's crystallized corpse in the Citadel throne room to demoralize Noctis. Nyx's kukris later appear as obtainable weapons in Insomnia.