King Fahn is the ruler of the holy kingdom of Valis and a central figure in the history of Lodoss, known as one of the six legendary heroes who defeated the Demon King and brought a temporary peace to the cursed island thirty years before the main story. Before ascending to the throne, he was a renowned knight of Valis who rose to lead the holy knights at a young age. His heroic status earned through the battle against the Demon King allowed him to succeed to the throne of Valis, a nation that traditionally chooses its king from the knighthood rather than by bloodline.

As a king, Fahn is portrayed as a wise and diplomatic leader. In contrast to his former comrade Beld, who seeks to unite Lodoss through military force from his base on the dark island of Marmo, Fahn works to bring the island together through peaceful diplomacy and alliances. He deeply values peace and order, yet he is also a man who carries significant personal burdens. Early in his reign, to appease the people of the northern deserts, he made the agonizing decision to hand over his newborn daughter, Princess Fianna, as a sacrifice to the dragon Shooting Star. This act haunted him, especially after his trusted knight, Tessius, secretly rescued the princess to spare the king further pain. Fahn agreed to the plan, which led to civil war, the independence of the nation of Flaim, and ultimately Tessius being sent to the front lines where he died in disgrace. Fahn carried the guilt of Tessius's death on his shoulders for many years.

His primary motivation is the protection and unity of Lodoss, guided by the ideals of peace and justice. This puts him on a direct collision course with Beld, whose invasion of the island culminates in an attack on Valis. Fahn's role in the story is that of a noble and tragic figure, the aging king and former hero who must stand against his greatest friend-turned-foe to defend his homeland. His personal history becomes intertwined with the journey of the young warrior Parn, who is revealed to be the son of the disgraced knight Tessius. When Parn arrives in Valis after rescuing Fianna, King Fahn has the opportunity to clear Tessius's name and restore his honor, mending a deep emotional wound for both the king and the young hero.

Key relationships define his character. His friendship with Beld is the most significant, a bond forged in the legendary war against the Demon King that transforms into a tragic rivalry as their philosophies for Lodoss diverge. He is a protective yet burdened father to Princess Fianna. His alliance with King Kashue of Flaim is crucial, as the two join forces against the Marmo invasion. The shadow of his guilt over Tessius connects him deeply to the story's protagonist, Parn.

In terms of development, King Fahn's arc is one of a hero facing his final, inevitable end. He is a static figure in the sense that his values do not waver, but the narrative reveals the heavy price of his kingship through the sacrifices he has made. His ultimate fate is sealed on the battlefield against Beld, where the two aging heroes duel. Fahn falls to Beld's demon sword, Soul Crusher, but Beld is immediately slain by an arrow from Karla the Grey Witch, allowing King Kashue to deliver the final blow. Thus, the War of Heroes ends with both legendary leaders dead, their grand visions for Lodoss unfulfilled in their own lifetimes. King Fahn is buried on the battlefield, and a later ceremony in Valis honors his memory.

As a warrior, Fahn is one of the most formidable of his age. He wields a Holy Sword, a white magical blade that is the direct counterpart to Beld's dark Soul Crusher. The two swords share a deep, mystical connection, and their clash on the battlefield is a fated event that decides the outcome of the war. His combat prowess, honed over decades of service as a knight and a legendary hero, makes him a peerless fighter, even in his old age.