Avan is a central figure in the story of Dragon Quest: Dai no Daibōken, initially appearing as a legendary hero and later as a mentor to a new generation of warriors. Fifteen years before the main events, Avan was the hero who defeated the Dark Lord Hadlar, bringing peace to the world. He hails from the noble family of the kingdom of Carl, and his full name is Avan de Zinuar III. His journey to defeat Hadlar began when the Dark Lord attacked Carl's castle, threatening Princess Flora, a close friend and his eventual love interest. This event prompted Avan to reveal his hidden talents and set out on a quest, accompanied by his best friend Roka, a knight of Carl. Over time, their party grew to include Leira, a priestess and rogue who would later become Roka's wife and the mother of Maam, and the powerful but eccentric Grand Sorcerer Matoriv. The martial arts master Brokeena also provided them with crucial support.

On the surface, Avan presents himself as a friendly, eccentric, and somewhat goofy individual who enjoys cooking and is not overly strict with his students. This lighthearted and seemingly scatterbrained demeanor masks his true nature as a highly intelligent, deeply thoughtful, and heroic person. This personality shift is a deliberate act of obfuscating stupidity, a habit stemming from his family history where an ancestor who was a prophet was feared and driven away, leading Avan to hide his capabilities to avoid being treated as an outcast. When the situation becomes serious, his frivolous manner falls away to reveal the resolute and courageous hero he truly is.

His primary motivation is the protection of the world and the nurturing of those who will inherit his will. After defeating Hadlar, Avan dedicated himself to becoming a tutor, seeking out and training disciples who could carry on his legacy. His students include Hyunckel, the first disciple; Maam, the daughter of his former companions Roka and Leira; and later, the young hero Dai and his friend Popp. His role in the story is that of a mentor and a symbol of hope. He re-emerges when the Dark Lord Hadlar is resurrected and begins training Dai. During a confrontation with the revived and more powerful Hadlar, Avan, exhausted from training and outmatched, performs a heroic sacrifice using a powerful suicide spell, Megante, in an attempt to destroy his old enemy and protect his students. Although believed dead, Avan survives thanks to a protective amulet given to him by Flora, but he remains in hiding for much of the story to allow his disciples to grow on their own without relying on him. He eventually reappears in the final arc to provide crucial assistance in the battle against the Dark King Vearn.

Avan's key relationships are foundational to the narrative. His bond with his disciples is one of deep care and faith in their potential. He serves as a posthumous (and later living) role model for Dai, who inherits his wish for world peace. His relationship with Princess Flora is a significant one, beginning as friends and developing into a romantic attachment, with her gift of a pair of glasses helping him hide his intelligence during his youth. His comrades from his original adventuring party, particularly Matoriv, remain loyal friends who continue to support his legacy years later.

In terms of abilities, Avan is an immensely powerful individual, often considered the strongest human of his era. He is a master of both swordsmanship and high-level magic, making him a true Magic Knight. He developed his own unique fighting style, aptly named the Avan Style, which focuses on training power, speed, and aura control. This style culminates in three specific techniques: the Earth Slash, representing brute force; the Wave Slash, representing speed and the ability to cut through energy and spells; and the Air Slash, representing the ability to cut invisible things and detect weak points. The ultimate technique of this style is the Avan Strash, a devastating attack executed with a reverse grip that combines all three principles. He can unleash this as a close-range cut, the Avan Strash Break, or as a long-range shockwave, the Avan Strash Arrow. Magically, Avan is proficient with spells such as Puff, which transforms him into a dragon, Kaclang, which turns targets to metal for protection, and he was able to cast a massive Megadestello barrier that purified Dermline Island. His most desperate spell is Megante, a suicidal explosion of incredible force. Beyond combat, Avan was a supremely effective instructor, devising rigorous training regimens like the Special Hard Course that dramatically increased his students' power in a short time. He was also a skilled craftsman, creating Maam's unique magic gun, and an excellent cook.