Nyx Ulric

Nyx is a young man with dark gray hair and blue eyes. He wears the black uniform typical of his fellow Glaives, but his is customized with a silver antler or horn on its hood, purple ribbons on its back, and pelts of blue-gray fur on its left sleeve. According to the The Art & Design of Final Fantasy XV book, the ornament indicates his heritage as a member of an ancient lineage of hunters and posits that it adds credibility to his role as a royal guard.

Nyx's signature weapon is his pair of kukris, one originating from Galahd and the other having been forged in Insomnia, symbolizing both of his homelands.

Nyx has small and subtle tattoos. He has a "crow's foot" on his right cheek and a line and a dot under his left eye. He has markings on his ears, intersecting lines down his neck, one around his right shin, and another around his left forearm. He also has a line down his middle finger of his left hand and another down his forefinger on his right hand. Although they can't be seen in the movie, a video showing a rotating 3D model of how his hair was rendered shows the tops of two tattoos on his back; two sets of intersecting lines, one over each shoulder blade.

Nyx appears with a large feline in some illustrations. It is a Galahd-native coeurl and Nyx's image-motif. Horns and fur on his gear symbolize him being wild and also foreign, as he is an immigrant from Galahd, thus from a different culture compared to Insomnia. His theme color is blue to complement Regis, whose purple theme reflects his nobility and maturity. To show Nyx's youth and to make it in line with Regis' purple, blue was chosen to be Nyx's color.

Nyx is a heroic individual who feels indebted to King Regis. He is confident in his abilities, but is haunted by the memory of his sister's death, which can cause him to have flashbacks during battles whenever his friends are in danger of not being able to save her. This is why he does all in his power to save his comrades, who call him by the moniker "hero" from his exploits. When his comrades betray him, Nyx remains loyal to the Lucian royal family, as well as his best friend, Libertus, and Lady Lunafreya; when Insomnia falls, he hangs onto hope and resolves to fight for the future thanks to Lunafreya's encouragement about his sister wanting him to see a brighter future.

Nyx is selfless, as he refuses to choose between Libertus or Lunafreya when requesting the power from the Ring of the Lucii. Nyx elects to instead sacrifice his own life to the past Lucian kings' spirits, who grant the ring's power to those they deem worthy. Nyx bargains with them, knowing that the price for using the ring's powers for those not of the Lucian royal blood is a life. Unlike his former mentor and superior, Titus Drautos, who was also General Glauca, Nyx can move on from his past to fight to help give the world a future, something that would not happen if Niflheim claimed the Ring of the Lucii instead of Prince Noctis. As a result, he was no longer fighting to protect Insomnia and did not care what happened to the city as long as he kept the Ring of Lucii away from the empire's hands.

Although he is selfless, it can be interpreted as arrogance, which leads to the old kings initially judging him as unworthy. Even when he proves his worth, Nyx gloats, saying that the kings would lose their "precious ring" if they burn him.

Nyx is a skilled wielder of the Lucian royal family's powers. He favors his ability to warp, which he does by throwing his kukris, as even though he is adept in close-range combat, the kukris offer him more range when thrown. As his powers are on loan from the king, he can lose them. Nyx uses various other types of magic, such as projecting fire and lightning from the palm of his hand and projecting magical shields. When deemed worthy of the Ring of the Lucii, he becomes even more powerful and gains the ability to control the Old Wall.

Nyx grew up alongside Libertus Ostium in Galahd, where they used to play as children in the Galahd River. Nyx and Libertus later ran a small bar in their hometown. The area used to be protected by the Wall, but thirty years ago, war overtook the lands and the Wall crumbled, allowing Niflheim to claim Galahd. Nyx fought in the local Resistance against imperial oppression, but his sister was killed and he was saved by King Regis of Lucis. Seeking to repay his debt to the monarch, after moving to the Crown City, Nyx joined the Kingsglaive, an elite unit of soldiers whose members are chosen for their aptitude for magic. He received training from Titus Drautos, who became the captain of the Kingsglaive. Due to their many great exploits together, Nyx came to view Drautos as a mentor.

“ My life is nothing. Giving the future to those who want to see it…is everything.”

Alongside his fellow Glaives, Nyx defends the borders of Lucis from Niflheim and Tenebrae's forces. When the enemy forces gain the upper hand through the use of Diamond Weapons, Nyx disobeys Captain Drautos' order to retreat and instead chooses to save Libertus from a Cerberus, a powerful three-headed beast. As punishment, Nyx is placed on guard duty upon his return to Insomnia, the crown city of Lucis. While on temporary duty, Nyx is bullied by royal guard Petra Fortis.

Three days before a peace treaty is to be signed between King Regis of Lucis and Emperor Aldercapt of Niflheim, Nyx is relocated to the Citadel by Drautos. As mentioned in Final Fantasy XV Prologue Parting Ways, Drautos has Nyx drop Noctis off at his place as thanks for using his car. The men discuss the death of Kingslaive infiltrator and friend Crowe Altius. The next day, Nyx gets into a heated argument with Libertus after seeing Crowe's corpse, which results in Libertus deserting the Kingslaive. That evening, Nyx attends a party celebrating the treaty-signing at Caelum Via and meets Princess Lunafreya. He passes a hairpin onto her that he had received among Crowe's possessions, knowing that giving it to Lunafreya had been part of Crowe's mission.

On the day the peace treaty is to be signed, Nyx discovers that Lunafreya has been kidnapped and Drautos has mysteriously disappeared. Nyx demands that King Regis deploy the Kingsglaive and leads his comrades on a mission aboard a Niflheim airship to rescue the princess after realizing that Crowe's watch, now in his possession, tracks the hairpin. However, Nyx is betrayed by a majority of his fellow Glaives who disagree with the peace treaty terms and deem that the king has abandoned them. Nyx frees Lunafreya and uses the airship to fly back to the Citadel with her. They witness the Wall fall as Niflheim begins its invasion, deploying daemons and magitek infantry to annihilate the city. Nyx and Lunafreya help a wounded King Regis escape Imperial General Glauca, who seeks the Ring of the Lucii, a ring that gives special powers to the past kings' chosen.

At the end of a secret passageway, Nyx questions King Regis' decision to sacrifice Insomnia for Prince Noctis' continued safety. Nyx agrees to protect Lunafreya, who Regis bequeaths the Ring of the Lucii to deliver to Noctis. Nyx flees with her while Regis stays behind to buy them time. He duels General Glauca, the commander of the Niflheim forces, and is killed after being impaled by Glauca's blade.

As he and Lunafreya drive away from the Citadel, Captain Drautos contacts Nyx and orders him to rendezvous with him in Section D of Insomnia. In the city plaza, fellow Glaive Luche Lazarus wounds Nyx. He is saved when Lunafreya kills Luche by tricking him to put on the Ring of the Lucii, which deems him unworthy and burns him alive. Drautos arrives, assisting Nyx and Luna, but he is suddenly crushed by Libertus' armored car. The two realize through Libertus's intervention that Drautos is actually General Glauca. The General summons his suit of armor and prepares to kill everyone. Nyx puts on the Ring of the Lucii and is granted its power in exchange for his life when the sun rises. After ordering Libertus to get Lunafreya somewhere safe, he gives her the ring to deliver to Noctis. Nyx engages Glauca in an epic battle while wielding the power of the old kings. In the clash's aftermath, Nyx manages to stab Glauca and dies peacefully as he wishes Noctis a healthy rule, his body turning to ash.

As depicted in Final Fantasy XV: Comrades, Libertus still holds onto hope that he will meet Nyx again. After the power of kings returns to the Glaives, Libertus migrates to Lestallum and leads the remains of the Kinsglaive in protecting the world in the king's absence. He writes a letter to Nyx about how daemons have done a number on Galahd, but he hopes that they can route electricity there one day.

Ten years after the world is plunged into darkness by the Starscourge, an illusory version of Nyx's corpse hangs in chains from the ceiling of the Citadel's throne room. Ardyn Izunia uses it to discourage Noctis. The corpse has white crystalline scarring, showing the damage that Nyx sustained by using the Ring of the Lucii. A psychomancer in the city holds Nyx's weapons and yields them to Noctis if defeated.