The Four Mamodo Prodigies were a group of four elite Mamodo children that only adults could possibly beat. They are sometimes dubbed as the undefeatable demon children and are mentioned by Keith in chapter 239, page 4.
Zeno Bell, eldest son of the royal family, received special training from his father for the duration of his life and also inherited his father's ruthlessness. Despite this, perhaps because of his relative isolation while training, he was the least famous of the four, as shown by Tia and Keith not recognizing him. Riou also did not recognize him immediately, but upon seeing his eyes and hair, he reacted with horrified shock.
Zeno's lightning spells were extremely powerful, and his partner Dufort's lack of empathy and Answer Talker ability made the two of them an impossibly strong team. However, Riou's last actions before they seized Faudo awakened Zatch's true power and caused Kiyo to gain the Answer Talker himself; these abilities combined with the help of their friends ultimately led to Zeno's defeat at Zatch's hands.
Brago is the most prominent of the four in the story, serving as a rival to the main protagonist Zatch. He received special training in the Mamodo World; the exact details are unknown, yet the results were shown in his ability to deflect unranked spells with his bare hands and endure a Dioga-class spell without much difficulty. Coldhearted and instilled with a desire for battle and more power, he was apparently the most famous of the four, his name and visage alone instilling fear in Tia, Kanchomé, Ponygon, Wonrei, Kido, Penny, and Zofis.
His partner in the battle was Sherry Belmont, whose introduction to the battle was when Zofis brainwashed her best friend Koko into a wicked, carnage-loving girl. They began on unpleasant terms; Brago saw all humans as inferior, and Sherry bore a coldhearted grudge against Mamodo-kind due to Zofis's actions. But with continual rigorous training and the determination to burn as many books as possible, she soon became a partner Brago could be content with. In time, they became close, Brago's heart softening with maturity while Sherry grew more determined to make him king.
All of the above along with the formidable element of Gravity ensured that Brago survived to the King's Festival, establishing neutral terms with the protagonists as time went by, most notably lending his aid against the battles with Faudo and Clear Note. Ultimately, he was the last adversary standing against Zatch, and after an exchange of their most powerful spells, Zatch stood victorious.
ElzadorElzador is the younger of the two rumored prodigies of the dragon clan, but very little is known about him or his partner, Abiira Sabiira.
They appear only in a flashback that shows their defeat at the hands of Vincent Bari and Gustav, the battle leaving Bari heavily scarred but with a new understanding of what strength truly means. Abiira was shocked and saddened to see his partner lose, but Elzador commended Bari for his strength.
AshuronAshuron is the elder of the two rumored prodigies of the dragon clan. The Scarlet scales that lined his body could repel or deflect the most powerful of spells, and his own abilities both physically and magically made him a very powerful foe.
Yet his own focus on achieving the throne lasted for a very short time; he was one of the first Mamodo to clash with Clear Note, and though he survived with just a scar, he learned of Clear's genocidal intentions and concentrated on training himself to stop him, to the point of ignoring the threat of the Ancient Mamodo despite his knowledge of them. To this end, once the King's Festival began, he tested Zatch's power and informed him of the threat of Clear. He ultimately sacrificed himself in an attempt to kill the evil Mamodo when they clashed once more, and though Clear survived, Ashuron injured him enough that he would require almost a year to recover. This bought the remaining Mamodo the time they needed to train to the level they needed to reach to defeat him. Ashuron shared his vision of harmony among Mamodo with Zatch before he faded, entrusting his will for the future to him. He took ninth place in the battle overall.
Reen Vise was Ashuron's partner. A relatively wise and very laid-back man who was initially skeptical about the battle, he was a loyal partner to Ashuron throughout his life, referring to the dragon as his master. He offered what assistance he could to Zatch and his allies following the dragon's return to the Mamodo World.