Bari, whose full name is Vincent Bari, is a seventeen-year-old mamodo, a supernatural being from another world who participates in a battle royale to determine the next king. He is a tall and powerfully built individual with a metallic, silver body that gives him a robotic appearance. His face is typically set in a fierce scowl, and his head is adorned with two large, bull-like horns. He wears a dark blue outfit reminiscent of a serious, intimidating jester's costume.

Bari's defining trait in his first appearance is his overwhelming and aggressive personality. He is a blood knight who lives for battle and seeks only to fight the strongest possible opponents. This obsession leaves him in a constant state of frustration and barely contained fury because no fight ever satisfies him. He holds nothing but contempt for weaker opponents, whom he defeats without mercy, and his only interest is in finding a rival who can challenge him. His fighting style is one of total offense, designed to crush enemies immediately without giving them a moment to counterattack.

However, this aggressive exterior masks a deeper need for purpose. Bari is driven by a desperate, unacknowledged search for meaning in his life and his battles. His initial motivation is simply to prove he is the strongest, but this goal rings hollow, leaving him perpetually dissatisfied. This changes following his encounter with the protagonists, Zatch and Kiyo. After a brutal battle where he easily overpowers them, he is moved by their unyielding determination and noble goal. This causes him to spare them and adopt a new purpose: to become a powerful and invincible king, a goal that gives his strength true direction.

Bari serves as a major obstacle and a turning point for the main characters, acting as a wake-up call that demonstrates the immense power of the remaining competitors in the tournament. After his character development, he transitions from a direct enemy into a powerful rival and crucial ally. His most significant relationship is with his bookkeeper, Gustav, a calm and wise Finnish man who contrasts sharply with Bari's fiery nature. Gustav acts as a parental figure and a stealth mentor, often remaining silent during battles but posing critical questions that force Bari to reflect on his actions and search for a higher purpose.

His key relationship with the protagonist, Zatch, begins with a one-sided rivalry, as Bari initially sees Zatch as a potential strong opponent to defeat. After their first battle, a mutual respect is forged, and Bari spares Zatch out of gratitude for giving him a new goal. This respect later culminates in Bari performing a heroic sacrifice, taking Zatch's place in a lethal trap to ensure his rival can continue fighting, a final act that completes his journey from a mindless brawler to a selfless warrior.

Bari's character development is one of the most pronounced in the series. He starts as a thoughtless thug who fights only for the sake of fighting, a past version of himself he later comes to hate. After being inspired by Zatch and guided by Gustav, he dedicates himself to finding true strength. This journey leads him to challenge a powerful dragon mamodo named Elzador. He emerges from this brutal training victorious but permanently scarred, having lost one of his horns and gained a new, profound understanding of what it means to be strong. He ultimately becomes a composed and powerful mamodo capable of striking even a king, fulfilling Gustav's wish for him to become a fine advisor rather than necessarily the ruler himself.

Bari's notable abilities all revolve around the manipulation of powerful vortices and spiral energy. His spell set is almost entirely offensive, reflecting his aggressive nature. Basic spells include Zonis, which fires a spiraling ray from his horns, and Garazonis, which turns his body into a spinning, drill-like projectile. He possesses several powerful variations, such as the arm-mounted drill spell Doruzonis and the massive, energy vortex projectile Gigano Zonis. For defense, he can summon Zorushield, a large metallic barrier. His most powerful spells include Dioga Zonisdon, an enormous and devastating vortex blast, and Amu Ra Zoruk, which enhances his hands with incredible strength, allowing him to catch and redirect enemy attacks. Bari is exceptionally durable, being one of the first characters to withstand the protagonist's ultimate lightning dragon spell, Baou Zakeruga, with minimal damage. He is noted as a naturally gifted and powerful mamodo, capable of defeating prodigies and becoming one of the strongest characters in the series without ever losing a fight.