Ironside is a central antagonist in the narrative, serving as a Holy Knight in the service of the Kingdom of Camelot and a member of an elite group known as the Four Evils. He is recognized by titles such as The Red Knight and Ironside the Assassin, reflecting his fearsome reputation and his bloody role as one of King Arthur's most trusted agents.

Physically, Ironside is a middle-aged man with a short beard, dark cyan hair, and a distinctive scar on his right cheek. His most recognizable feature is his suit of red armor, which includes a unique frog-mouth helmet with three crooked visors and a high-collared cape, giving him an imposing and sinister silhouette. When he unleashes greater power using a fragment of Chaos, he can enter a full Chaos Form where he grows two additional sets of arms and an extra eye in each of his helmet's visors.

The personality of Ironside is defined by a chilling ruthlessness and a nearly impassive demeanor. He is capable of committing brutal acts, including the murder of his own father, with an absolute lack of visible emotion, all while claiming that his actions serve the greater good. He holds no regard for the lives of innocent people, as demonstrated when he attempted to sacrifice the entire town of Sistana to activate the Coffin of Eternal Darkness. His callousness extends to Percival, a boy he raised, for whom he has no love, compassion, or regret, a fact that is confirmed by another character's magic power that can detect lies and true intentions. Despite this cruelty towards almost everyone else, Ironside displays a contrasting, calmer, and caring side towards his biological son, Diodora, and his brother-in-law, Mortlach. He is protective and respectful of them, seeing them as his true family.

Ironside’s primary motivation is an obsessive desire to save his son, Diodora. Diodora and his mother fell victim to a terrible illness caused by the Demon King's poison from a previous holy war, which resulted in the mother's death. To cure his son, Ironside returned to the service of Arthur Pendragon, believing Camelot held the only opportunity to save Diodora. His desperation led him to a forbidden spell from the Spirit Arts. He found the deceased infant of a royal family, who would later be named Percival, and intended to use the child's body as a vessel for a powerful Life Spirit. His plan was to transfer Diodora's soul into this new, nearly immortal body, so his son could live for close to a millennium.

His role in the story is set in motion when his father, Varghese, betrayed Camelot and fled with the infant Percival, who had unexpectedly gained self-awareness and was thus no longer a suitable vessel. This act ruined Ironside's plans and filled him with a deep, seething anger. In the present, Ironside, now under orders to eliminate the prophesied Four Knights of the Apocalypse who are destined to doom King Arthur, tracks down Varghese. He kills his own father without hesitation and attempts to murder Percival, whom he now views as worthless and a threat that must be eliminated.

Several key relationships define his character. With Varghese, his relationship is a twisted one where lingering professional respect exists, but all filial bonds have been severed by betrayal and violent patricide. Toward Percival, he harbors no paternal feelings whatsoever, only seeing him as a failed experiment whose very existence is an obstacle. In stark contrast, his relationship with his biological son, Diodora, is one of obsessive love and devotion, with Ironside willing to sacrifice his own lifespan and commit terrible atrocities to secure his son's future. As one of the Four Evils, he also works alongside other powerful knights like Pellegarde, though his ruthlessness even leads him to attack his allies when they fail to follow his uncompromising logic.

In terms of development, Ironside undergoes a transformation in his pursuit of power. After receiving a fragment of Chaos from King Arthur, he gains immense new abilities at the cost of part of his humanity and his memories, becoming only partially human. This choice further distances him from any remaining empathy and solidifies his role as a terrifying agent of Camelot.

As for his notable abilities, Ironside is considered one of the most powerful Holy Knights in Camelot. He is an excellent swordsman, able to easily block blows from both his experienced father and other skilled fighters. He also possesses a phantom boat for air travel, which only he can use. His primary form of attack is a unique magical power that projects invisible, star-shaped wind slashes. He can create these powerful cutting attacks simply by pointing or swiping his fingers, capable of severely wounding or killing a person and carving up bedrock. His mastery of Spirit Arts is advanced enough to summon and control high-ranking elemental spirits. Most notably, he can summon Djinn, the King of Wind, a colossal being that he can command to perform techniques like surrounding himself and his enemies in a wind barrier for a finishing blow. He was also able to perform a Forbidden Spell to summon a Life Spirit, a feat that came at the great cost of much of his own lifespan.