The character Hadler is introduced as the initial primary antagonist whose legacy sets the stage for the conflict. Before the main story begins, Hadler was the Demon Lord who once attempted to conquer the world before being defeated by the hero Avan. This original defeat had a liberating effect, as it freed the world's monsters from his evil influence, allowing them to live peacefully.

Hadler's return marks the inciting incident of the narrative. He is resurrected from death by the Great Demon Lord Vearn, a far more powerful entity, and coerced into becoming the leader of Vearn's Dark Army. This resurrection is not a second chance at independent conquest but a subjugation, as Hadler is forced to serve a master stronger than himself. His revival also carries a more personal and cruel dimension, as he announces his return by attacking his former nemesis, Avan, who is now training a new generation of heroes. During this confrontation, Avan sacrifices himself in a failed attempt to destroy Hadler, solidifying the villain’s role as the direct threat that the protagonist, Dai, must overcome.

Beyond his function as a powerful enemy, Hadler is a character who evolves beyond a simple evil archetype. While initially presented as a formidable and menacing Dark Lord, his position under Vearn introduces a layer of complexity. As the series progresses, he is shown to possess a personal code of honor and faces his own internal struggles regarding his state as a resurrected servant. This development ultimately transforms him from a straightforward villain into a more nuanced figure who plays a crucial and unexpected role in the narrative's final arc.

Regarding his specific motivations and personal history, the search results do not provide detailed information. While his role as the reinstated leader of Vearn's army is clear, his personal feelings about this servitude and any backstory beyond his original defeat remain unverified. Similarly, detailed descriptions of his key relationships with other members of the Dark Army, such as the generals Myst-Vearn or Zaboera, are not available. Any comprehensive list of his notable abilities, including his signature spells or physical powers, could not be reliably sourced from the provided material.