Brago is a mamodo, a child from the Mamodo World, who participates in the battle to determine the next king. He is fourteen years old and has a pale, gray complexion with an angular, menacing face. His spiky black hair is streaked with hints of purple, and he has narrow eyes with black sclera that intensify his threatening demeanor. He typically wears a long, ragged black fur cloak with jagged purple undertones and black boots with silver accents, giving him a gothic appearance.

Brago is characterized by his quiet, antisocial, and brooding nature. He rarely socializes with other mamodo, with many, such as Tia and Kanchome, fearing him due to his immense power and reputation as one of the strongest among them. He is known for being extremely strong-willed and resents weakness, both in others and initially in himself for requiring a human partner to read his spells. He has a ravenous appetite, a trait common among mamodo. His core motivation is to become a powerful and strong king. He desires to rule with his own strength and has expressed that if villains were to appear in the Mamodo World, he would deal with them personally rather than rely on any special privileges of the king, which he finds boring.

In the story, Brago and his human partner, Sherry Belmont, serve as recurring rivals to the main characters, Zatch and Kiyo. Despite their limited number of direct confrontations, they are considered one of the most powerful teams in the series, having destroyed more spellbooks than most other participants. They ultimately become the runners-up in the battle to decide the king. Brago plays a significant role in helping Sherry rescue her friend Koko from the evil mamodo Zofis, a turning point that deepens their partnership. In later arcs, he reluctantly teams up with Zatch and the others to combat greater threats, such as the living giant Faudo and the immensely powerful mamodo Clear Note, showcasing his willingness to cooperate against a common enemy.

The central and most defining relationship for Brago is with his bookkeeper, Sherry Belmont. Initially, their partnership is volatile and antagonistic. Brago is portrayed as vicious, heartless, and bloodthirsty, believing that human weakness is a hindrance. He once threatened to harm Sherry's butler to force her to discard her sympathy, prompting Sherry to threaten her own life to keep him in line and assert that he should never underestimate humans. Over time, however, Brago's attitude softens considerably due to Sherry's influence. Despite occasionally complaining that she is too weak, he develops a deep and genuine care for her. This change is demonstrated in small acts, such as suggesting she rest under the guise of her being too slow, and in major moments, such as when he thanks her for being his partner during their final battle. In that battle, when Sherry is willing to sacrifice her life for his victory, Brago refuses to allow it, grabbing her hand and causing her to drop the spellbook, accepting defeat and expressing his gratitude and happiness to have had her as a partner.

Brago experiences significant character development throughout the series. He begins as a selfish, borderline psychotic individual who views power as the sole objective and despises his reliance on a human. Through his journey with Sherry, he evolves into a nobler person who values companionship and cares about the feelings of others. He is even seen helping a human child find courage and strength, a moment that brings a rare smile to his face, though he denies it when questioned. By the final battle, he has let go of his purely selfish ambition for the throne, ultimately prioritizing Sherry's life over his own chance to become king. As part of his development, he also learns to cooperate with rivals like Zatch and Kiyo without complaint, particularly in the battle against Clear Note.

Brago possesses immense physical strength, often defeating other mamodo teams without even using his spells. His specialty is gravity magic, which manifests as dark, destructive spheres that can crush opponents and devastate large areas. His power grows throughout the story as he and Sherry unlock new spells. He has shown the ability to slice through multiple mountains and tank powerful attacks. Brago is considered one of the four elite mamodo prodigies, a group said to be so powerful that only adult mamodo could defeat them. Among his most notable abilities is the capacity to draw power from the Earth's rotational energy to amplify his spells, making him a continent-level threat on par with Zatch's most powerful attacks. In training for the final battles, he further enhanced his gravity powers by training in areas with strong magnetic fields.