Vearn, supreme ruler of the Underworld known as the Dark King or Great Demon King, stands as the primary antagonist. An ancient darkling, he seethed with resentment toward humanity for inhabiting the sunlit surface while his kind languished in darkness. This drove his millennia-spanning ambition to obliterate the surface realm and redirect sunlight below, aspiring to godhood to rectify what he deemed divine injustice.

To secure immortality for his grand design, Vearn employed a secret spell to split his body. One half remained eternally youthful through the Secret Spell of Frozen Time, maintained during solar eclipses; the other aged, accumulating vast magical power. He entrusted his frozen form to the monster Myst, birthing the formidable warrior Mystvearn as his bodyguard. Vearn coexisted under a truce with his rival Velzar, the Abyss Dragon King, each pursuing world conquest independently.

Establishing the Dark Army, Vearn revived the fallen Dark Lord Hadlar as Supreme Commander, enhancing his body and granting command. Yet, he implanted a Black Core within Hadlar—a continent-destroying bomb detonatable remotely—as insurance. This act later spurred Hadlar's betrayal, perceived as cowardice. Vearn manipulated others similarly: recruiting Dragon Knight Baran by exploiting his hatred sparked by Alkeed's destruction, and accepting Killvearn, Velzar's disguised assassin, viewing him as an entertaining challenge.

Initially concealed behind a veil, Vearn presented a frail, elderly humanoid guise: beige skin, long white beard, black horns, and a forehead third eye (the Sovereign Rock). This unassuming appearance masked his true nature, causing allies and foes to underestimate him. His true form emerged after merging with his youthful half: a towering, muscular silver-haired demon retaining the third eye, discarding his staff for physical combat. As a final gambit, he plucked the Sovereign Rock, transforming irreversibly into the Sovereign Supreme—a gargantuan, armored beast with crustacean-like physiology and rock protrusions, sacrificing original abilities for overwhelming power.

Vearn's personality melded calculated patience with absolute social Darwinism. He deemed power the universe's sole law, dismissing human morality as weakness. Despite genocidal aims, he displayed pragmatic fairness: rewarding subordinates like Hadlar for growth and granting multiple redemption chances, though ultimately viewing them as expendable tools. A skilled chess enthusiast, he orchestrated strategic conflicts, deploying traps like the Loroi Valley execution plot to ensnare enemies. His cruelty manifested in sadistic enjoyment of despair and speeches designed to shatter opponents' ideals.

Magically, Vearn wielded peerless prowess honed over millennia. Signature spells included Kaiser Phoenix (a fiery bird Kafrizz variant) and instant-cast Boom spells rivaling Kaboom's devastation. Unique techniques encompassed Aura Shot for destructive energy bursts and Calamitous Wall for shockwave attacks. The Staff of Edacity converted magic into physical strength, shattering orichalcum at the cost of continuous mana drain. Fusing with his youthful body granted close-combat prowess: Phoenix Wing deflected attacks barehanded, while Demonic Guard of Heaven and Earth countered multiple assaults simultaneously. His third eye imprisoned weaker foes or forcibly evolved monsters; its destruction triggered his Sovereign Supreme transformation. As a darkling, he possessed three hearts, regeneration, and survival with only one heart intact.

In the final conflict, Vearn confronted Dai after the hero inherited dual Dragon Crests. Forced into his Sovereign Supreme form, he battled Dai in orbit. Defeat came when humanity's collective hope empowered Dai's strike, catapulting Vearn's remains toward the sun—an ironic end for one consumed by sunlight obsession.