Hadlar is a central antagonist in the anime and manga series, serving as the initial primary threat before the revelation of an even greater evil. His background is rooted in a failed conquest. He was originally the Demon Lord who once tried to rule the world, only to be defeated and killed by the hero Avan. In the wake of his defeat, the monsters under his control were freed from his evil will, leading to a period of peace. However, Hadlar is resurrected by the Great Demon Lord Vearn, a more powerful being to whom he then swears allegiance. This resurrection transforms him from a defeated tyrant into the commander of Vearn's army, tasked with once again conquering the world of humans.

As a character, Hadlar is defined by his immense pride and arrogance. He is a classic dark lord who craves power and dominion, but his personality is more nuanced than simple cruelty as the story progresses. Initially, he serves as a direct and brutal threat, confronting Avan and his disciples soon after his return. His motivations are driven by a desire for power and a hunger to prove his strength, yet his servitude to Vearn creates a interesting dynamic. Despite his position as a subordinate, his ambition remains a core trait. Key moments in the narrative reveal a growing respect for his enemies, particularly the young hero Dai, marking a significant evolution in his role from a one-dimensional villain to a more complex rival.

Hadlar’s role in the story is as the primary engine of conflict at the beginning. His resurrection and attack on Avan set Dai and his companion Pop on their journey. As the commander of the Demon Lord’s Army, he leads six powerful regiments, each led by a formidable warrior like Crocodine, Flazzard, and Baran. His relationship with his master, Vearn, is one of fearful loyalty, while his relationships with his own subordinates are based on authority and a shared goal of conquest. His most important relationship is with Dai, as he serves as a direct foil and a recurring obstacle that the hero must overcome, and in their final confrontation, a mutual warrior’s respect is established.

Throughout the series, Hadlar undergoes a significant transformation, both in power and character. After being resurrected, he finds his new body is still not strong enough to defeat Dai and his friends. To rectify this, he undergoes a transformation into a hyper demon, granting him a massive increase in strength and powerful regenerative abilities. This new form allows him to become a much more formidable combatant. His development is not just physical; he evolves from a boastful lackey into a fierce warrior who values strength and honor, culminating in a final battle where his body is damaged beyond its ability to regenerate, and he turns to dust. He also displays cunning as a strategist, such as when he uses forbidden magic on five pieces of Orichalcum to create his elite Orhicalcum Royal Guard warriors.

In terms of abilities, Hadlar is a highly powerful magic user and combatant. He is especially proficient in destructive magic, with his strongest spells being Kaboom, a high-level explosive spell, and Kasizzle, the most powerful form of fire magic. After transforming into a hyper demon, his physical strength, speed, and durability increase dramatically, and he gains a potent healing factor that allows him to regenerate from severe injuries. His signature weapon is the Sword of Champions, and in his enhanced state, he specializes in dealing overwhelming physical fire-based attacks. Even before his transformation, he was strong enough to survive a self-sacrifice spell from his former conqueror, Avan, showcasing his immense durability.