Karkinos Lucan is one of the Nodos, powerful beings who have formed a contract with the Silver Tribe, and serves as a significant figure within the narrative of Heroic Age. He hails from a race known as the Hydras, and the Heroic Tribe entity that dwells within him is named Lerneia. His appearance is distinctive and somewhat unconventional, characterized by long white hair, prominent cheekbones, and a face that appears more mature and weathered than the typical youthful hero. This unique design, combined with his persistent antagonistic role, made him a notable presence throughout the series.

In terms of personality, Karkinos is defined by his calm, rational, and quiet disposition. He is a deliberate thinker who is not easily provoked to rash action or visible displays of emotion. This rationality is central to his character, as he approaches his duties and conflicts with a level-headed perspective. However, this strength is also a flaw; he is described as being somewhat clumsy when it comes to understanding emotional nuances, often failing to grasp the feelings and intentions of others, most notably the character Yuty La. Despite this emotional blind spot, he harbors deep-seated feelings for Yuty, frequently stating his desire to protect her, even when such actions are not mandated by the terms of his contract.

His primary motivation is rooted in the four labors, or the contract, he has sworn to the Silver Tribe. This contract binds him to several key obligations: to swear allegiance to the Silver Tribe, to fight to the death against any who oppose them, to save any fellow Nodos of the Silver Tribe who is in mortal danger, and to serve until the Silver Tribe obtains the power of the Golden Race. These vows drive his actions throughout the story, compelling him to confront anyone he perceives as a threat to his masters. He is the first Nodos to engage the protagonist, Age, in battle, and over the course of the series, he becomes the Nodos who fights and is defeated by Age more frequently than any other. This recurring pattern of conflict and defeat forms the core of his role in the story, positioning him as a persistent rival.

Karkinos's most significant relationship is with Yuty La, a member of the Silver Tribe. Their connection is delicate and complex, defined by his inability to fully comprehend her emotions yet his unwavering commitment to her safety. Conversely, Yuty, who generally considers emotions unnecessary for existence, is most strongly affected when Karkinos is involved. This bond is so profound that her emotional control fractures, leading her to a state of frenzy when Karkinos is killed in battle. This relationship, where a seasoned warrior is tethered to a young, powerful Silver Tribe member, adds a layer of personal stakes to his otherwise duty-bound actions.

Throughout the series, Karkinos undergoes a subtle but meaningful development. His repeated defeats at the hands of Age, rather than fostering only hatred, seem to open a door to a different perspective. In his final encounter with Age, when the protagonist extends a hand in an offer of peace or alliance, Karkinos is visibly taken aback, suggesting a shift in his understanding of his role and his enemies. This moment hints at a breaking of his rigid adherence to conflict, showing a character capable of change when faced with genuine outreach.

As a Nodos, Karkinos possesses formidable abilities that reflect his connection to the Heroic Tribe. His Nodos form, Lerneia, is purple in color and wields the power of Restoration. His primary method of attack involves employing a potent corrosive gas that is implied to have the power to destroy entire solar systems. In addition to this devastating offensive capability, Lerneia can transform into a type of hydra when on solid ground, referencing the mythological creature from which his Heroic Tribe's name is derived. Furthermore, he possesses the ability to be resurrected, a power that likely contributes to his repeated confrontations with Age.