Clevatess is one of the four great beast kings who serve as living barriers, sealing off the borders of the world of Edsea and keeping humanity confined within the continent. Known as Clevatess of the Moonlight, this being rules over the southern lunar mountains and is feared as the Dark King of the South. In its true form, Clevatess appears as an immensely powerful giant black wolf adorned with a pair of large ram-like horns, a single unicorn-like horn on its forehead, and approximately seven tails tipped with barbed carapaces that possess incredible reach and strength. A mane that shines like moonlight grows from its head to its chest.

For centuries, Clevatess lived as an isolationist, showing no interest in humanity and never deliberately attacking human settlements. However, approximately a thousand years after the last human intrusion into its territory, a kingdom dispatched thirteen heroes to slay the beast king. Clevatess slaughtered all of them with brutal efficiency and, as retaliation for the unprovoked attack, launched a direct assault on the capital of Haiden. The beast king razed the city, slew the king, and nearly obliterated the entire country. As Clevatess stood on the brink of erasing all humans from Edsea, a dying boy named Shiro Creitos, who was shielding an infant prince beneath rubble, made a plea. The boy asked Clevatess to take the baby, proposing that if the beast king protected and raised the child, it would prove humanity's worth. Taken by curiosity or whimsy, Clevatess agreed to this bargain.

Clevatess is characterized by a personality that is calm, intelligent, and deeply arrogant, yet also marked by a surprising flair and a strong sense of honor. As a beast king, Clevatess holds a very low opinion of humans, previously dismissing the race as beneath notice. Unencumbered by human custom or morality, the creature observes human behavior with clinical indifference, cataloging hypocrisies where a typical person might moralize. Despite this capacity for genocide, Clevatess operates according to a personal code, believing that as a king, certain standards must be upheld, and a promise once made will not be broken even for pragmatism. The beast king finds needless cruelty distasteful, viewing death as a natural part of life rather than a source of sadistic amusement. This moral framework, while alien by human standards, grants Clevatess a peculiar form of integrity.

After taking the infant, whom Clevatess named Luna, the beast king quickly realized having no knowledge of how to raise a human child. Knowing nothing about childcare, Clevatess resurrected one of the slain heroes, a woman named Alicia Glenfall, by infusing her corpse with demonic blood. The reasoning was straightforward: as a female, Clevatess assumed she could feed the child, though this assumption proved embarrassingly incorrect. Nevertheless, Alicia became bound to Clevatess as a follower, forced to care for Luna and provide information about the human world. To travel through human society without causing an uproar, Clevatess adopted a human disguise named Clen, taking the form of a young dark-haired boy modeled after the dying youth who had entrusted Luna to the beast king's care. In this form, Clevatess's power is significantly diminished, with defensive capabilities reduced to ordinary human levels, though the true form remains hidden within Clen's shadow.

Clevatess's initial motivation for raising Luna was essentially an experiment: to observe whether humanity deserved extinction or mercy, using the child's development as a metric. The plan was to install Luna, who was revealed to be the last pure-blooded heir to the fallen kingdom's throne, as a puppet king, thereby transforming the human world into a chessboard under the beast king's control. However, as the journey progresses, Clevatess becomes increasingly attached to the infant, shifting from a pragmatic caretaker to something resembling a protective guardian. This development is gradual but significant, with Clevatess scolding Alicia when she is not attentive enough to Luna's needs and ultimately finding the child's well-being a matter of genuine concern rather than mere utility.

The relationship between Clevatess and Alicia forms a central pillar of the narrative. Their dynamic is one of tense dependence, marked by jagged exchanges and mutual exasperation. Alicia was resurrected against her will, forced to serve the being who killed her, and yet the two must cooperate to care for Luna. Clevatess dismisses human morality as a fallacy, while Alicia stubbornly refuses to surrender her sense of right and wrong, carrying the scars of her death and resurrection as both physical and emotional burdens. Through this partnership, Clevatess begins to encounter human resilience in forms that challenge its initial verdict on humanity's worth. Encounters with other characters, such as the abused slave Nelluru who becomes Luna's wet nurse, further influence the beast king's changing views. Even Clevatess finds the mistreatment of slaves and the murder of newborn infants heinous, suggesting a capacity for something resembling empathy or at least a consistent ethical framework.

Clevatess wields immense power befitting one of the four beast kings. Physical abilities include superhuman strength and speed sufficient to slaughter thirteen heroes with a mere swing of its tails and to traverse the distance from its mountain domain to the capital before nightfall. The creature has mastery over shadows, able to manipulate its own shadow to consume people, teleport through the shadows of enemies, and store objects or parts of its body within darkness. The multiple barbed tails are devastating weapons capable of puncturing steel armor. Clevatess also possesses necromantic abilities, capable of raising the recently deceased by infusing their corpses with its blood, creating bound followers who carry its power within them. Additionally, Clevatess can transfer energy to maintain the physical strength of other life forms and can heal the dying by mixing its blood and flesh with theirs. The beast king demonstrates a sharp analytical mind, able to assess combat mechanics and magical principles with minimal prior exposure. This combination of raw power, tactical intelligence, and a millennia-old perspective makes Clevatess an entity that is not merely strong but genuinely formidable on every level.

As the story unfolds, Clevatess is guided by curiosity beyond the original experiment with Luna, venturing out of the southern mountains to seek answers about the world's mysteries, the true history of the legendary heroes, the purpose of the beast kings themselves, and why they must enclose humanity. The once absolute convictions of this ancient being gradually begin to shift through each experience and growing bond. Clevatess finds poignancy in the collision between its own detached, observational perspective and the painful, felt reality of human lives. The beast king is not softened by the task of raising a child so much as intrigued by it, treating the entire endeavor as a thought experiment that slowly transforms into something more meaningful. Through all the violence and contemplation, Clevatess becomes a study of what happens when a being of immense destructive power pauses long enough to consider what it might mean to care for something small and fragile and human.