Lux Arcadia was born as the illegitimate seventh son of Emperor Diseld Arcadia, alongside his younger sister Airi. Unlike his half-brothers, Lux was often scorned within the imperial court, receiving little recognition despite his natural talent. Much of his early life was spent in seclusion under private tutelage, while also caring for the frequently ill Airi.

At the age of eight, Lux met the merchant Dalto Aingram, whose late wife had been a close friend of Lux’s mother. Through this connection, Lux befriended Dalto’s daughters, Relie and Philuffy. His bond with Philuffy deepened after he took the blame for a broken statue that had been damaged by his half-brother Abel and his companion Ragreed.

Soon after, Lux’s maternal grandfather, Wade Roadbelt, publicly criticized the emperor’s policies. In response, Emperor Diseld had him imprisoned and banished Lux and his mother from the court. Forced to live on the outskirts of the capital, Lux and his mother became targets of public resentment. When Lux was ten, their carriage fell off a cliff. Though Lux pleaded for help for his fatally injured mother, the nearby citizens jeered at him and pelted him with stones, resulting in her death.

The loss filled Lux with hatred toward others, and he even pushed Philuffy away. Nevertheless, Philuffy continued to visit his mother’s grave daily, offering flowers and comforting him. Her persistence allowed Lux to let go of his bitterness, and before leaving the capital with her family, Philuffy inspired him with the hope of creating a world where girls like her could live in peace.

By the age of twelve, Lux had already become the youngest Drag-Knight in history, winning hundreds of victories in mock battles. Despite this, he received little recognition due to his illegitimacy and outspoken opposition to the Old Empire’s policies. During this time, he also developed the secret Drag-Knight technique Quick Draw.

Five years before the main story, the Old Empire began conducting human experimentation on young girls to create living weapons, one of whom was Philuffy Aingram. Around the same period, Count Atismata and allied lords organized a rebellion with support from neighboring nations. Encouraged by his older brother Fugil, Lux secretly joined the uprising in an effort to save Philuffy. Unbeknownst to the rebels, however, Count Atismata’s sister Raffi betrayed them by revealing their plans to the emperor.

Lux eventually learned that Philuffy had perished from the experiments, a discovery that drove him to despair. Determined to take revenge, he resolved to assassinate the emperor himself, only for Fugil to intervene and use Ouroboros to alter his memories. Together, Lux and Fugil devised a strategy to infiltrate the imperial capital, capture the imperial family, and open the gates to Count Atismata’s forces. To increase his combat endurance, Lux underwent the Baptism ritual performed by the automaton Arshalia Rei Arcadia, allowing him to wield Bahamut at greater capacity.

On the rebellion’s final day, Emperor Diseld attempted to use Airi as a hostage. Fugil intervened, rescuing her and summoning Ouroboros once again. Donning Bahamut, Fugil defeated the empire’s army and urged Lux to slay the imperial family, declare himself emperor, and assume responsibility for the coup. Lux refused and fought his brother, but was defeated. Fugil then rewrote the memories of those present, making it appear that Lux had annihilated 1,200 Drag-Knights of the Old Empire without killing them. This false narrative gave rise to the legend of the Black Hero.

In the aftermath, Lux and Airi were branded criminals as the last known survivors of the Old Empire. Though pardoned, they were burdened with a massive debt equal to one-fifth of the New Kingdom’s national budget. Lux worked menial jobs to repay it, while Airi assisted by decoding ancient manuscripts and updating Drag-Ride manuals at the Royal Officer Academy, where she was also held as a hostage to ensure Lux’s compliance.

To secretly train with Bahamut, Lux used a heavily modified Wyvern Drag-Ride, weighted to mimic Bahamut’s performance. In practice matches, he focused solely on defense, never striking back but always avoiding defeat. This cautious style earned him the nickname Weakest Undefeated.

Lux is depicted as a handsome young man with silver hair and gray eyes, distinguishing features of the Arcadia imperial bloodline. As a remnant of the fallen empire, he wears a black collar imposed by the New Kingdom of Atismata to signify his servitude and status as a former criminal.

His usual attire is the men’s uniform of the Royal Officer Academy, a set specially prepared for him by Relie Aingram. On rare occasions, Lux has been shown in alternate attire. Notably, during his encounter with Celis, he was forced to disguise himself in the female academy uniform, wearing a straight black wig and adopting the alias “Luno.”

Lux is characterized by his kindness and willingness to help others, guided by a strong moral code. During the rebellion against the Old Empire, he sought to avoid killing his enemies whenever possible. According to Magialca Zen Vanfrick, this approach, though more difficult, enabled Lux to gain allies and trust beyond what most in his position could expect, reflecting his natural charisma. His compassion and integrity earned him the respect of the Royal Officer Academy’s students, many members of the Seven Dragon Paladins, and the citizens of the New Kingdom. Ultimately, he was even considered a candidate for kingship due to his ability to unify others.

Despite his reputation, Lux is shy and easily flustered around girls his age, a trait complicated by his unique position as the only male student at the academy. Many of the girls frequently ask him to complete odd jobs, further playing on his modest and accommodating nature.

While generally gentle and reserved, Lux can adopt a serious, calm, and calculating demeanor in battle. Krulcifer notes that when provoked, he is capable of unleashing an aggressive and destructive side that contrasts with his usual composure. He has also demonstrated insight and foresight that often surprise those around him.

Lux’s personality is further shaped by his persistence and stubbornness. As Airi observes, once he decides to help someone, he does so regardless of the risks, even at the cost of recklessness. He openly admits to having a tendency to show off, often pushing his body past its limits in pursuit of a victory where no lives are lost.

For years following the fall of the Old Empire, Lux carefully concealed his identity as the Black Hero by portraying himself as a purely defensive fighter. This façade of weakness allowed him to avoid suspicion while steadily refining his abilities in secret.

Lux Arcadia is regarded as an exceptionally skilled Drag-Knight. He was the youngest Drag-Knight in the history of the Old Empire, earning his license at the age of twelve. Under the New Kingdom, his defensive style in mock battles allowed him to avoid injury entirely, earning him the nickname Weakest Undefeated. Over time, Lux has defeated several powerful enemies, including three different Ragnaroks and even the Sacred Eclipse.

Baptism
Lux has undergone Baptism on four separate occasions, each granting him new abilities:

• First Baptism: Conducted by Fugil before the fall of the Old Empire, granting Lux the ability to analyze opponents’ attacks, movements, and thought patterns with near-future predictive accuracy.
• Second Baptism: After sacrificing himself to protect Yoruka, Lux was resurrected by Sacred Eclipse, gaining enhanced stamina.
• Third Baptism: Performed by the android Arshalia during the Avalon trials, increasing his concentration abilities to a significant degree.
• Fourth Baptism: Administered by Aeril during the Rebellion Arc, granting him a perception-based disguise ability, allowing him to alter his appearance to others.

Combat Skills

• High Drag-Ride Aptitude: Despite being male, Lux possesses an unusually high affinity for Drag-Rides, enabling him to operate even a Divine Drag-Ride for extended periods. His aptitude is attributed to both his imperial lineage and the Baptisms he has undergone.
• Swordsmanship: Lux is an accomplished swordsman, capable of precise strikes that target Drag-Rides’ weak points, such as arms, Force Cores, and Sword Devices without harming the pilots. His mastery enables him to subdue entire armies of Drag-Knights without inflicting fatalities.
• Throwing Weapons: While piloting Bahamut, Lux demonstrates expert skill with thrown objects, launching them with such force and accuracy that they rival bullets in speed, capable of disabling Drag-Rides even while engaged in combat with larger threats like Ragnaroks.

Techniques

• Break Purge (機竜解放ブレイクパージ, Drag-Ride Liberation): A fundamental Drag-Ride operation that involves purging portions of its weaponry and armor. The released armor fragments scatter like buckshot, obstructing an opponent’s vision and disrupting their attacks. While effective, the technique reduces barrier strength and mobility, making it risky in prolonged combat. Lux has refined the technique for advanced use, allowing him to switch Drag-Rides mid-battle.

Drag-Rides
Lux’s primary Drag-Ride is the Divine Drag-Ride Bahamut, a jet-black wyvern-class Drag-Ride marked by glowing red veins. It places an immense stamina demand on its pilot, to the extent that Lux often trains using a modified Wyvern adjusted to Bahamut’s weight and resistance before deploying the Divine Drag-Ride in actual combat.

Airi Arcadia
Lux’s younger sister and the only other surviving member of the Old Arcadia Empire’s imperial family. He is deeply protective of Airi, having cared for her during their childhood when she was often ill. Although Airi sometimes criticizes Lux, she trusts him completely and worries about his well-being. Their bond remains central to Lux’s sense of responsibility and moral drive.

Lisesharte Atismata
The princess of the New Kingdom Atismata and one of Lux’s closest companions. Their first meeting occurs when Lux accidentally intrudes into the women’s dormitory bathhouse, sparking a complicated but ultimately close relationship. Over time, Lisesharte comes to trust Lux and relies on his support, with their bond carrying both political and personal significance.

Philuffy Aingram
Lux’s childhood friend and one of his most important emotional anchors. Philuffy comforted Lux during his grief after his mother’s death, visiting her grave daily and helping him move beyond his hatred. Before leaving the capital, she inspired Lux to create a world where girls like her could feel safe. Their relationship remains deeply significant, with Philuffy continuing to serve as a symbol of his ideals.

Fugil Arcadia
Lux’s eldest half-brother and a central figure in his past. Fugil played a crucial role in shaping Lux’s path, manipulating events during the rebellion and using Ouroboros to alter memories, including Lux’s own. Although Fugil’s interventions helped bring down the Old Empire, his methods and ambitions placed him at odds with Lux, creating a complex relationship of admiration, resentment, and rivalry.

Nulph
The prime minister of the New Kingdom, who keeps a close watch on Lux and Airi after the fall of the Old Empire. While ostensibly a political overseer, Nulph represents the pressure of the new regime, as Lux is constantly aware of being monitored and used as a tool for the kingdom’s stability.