Isol is the commander of the Mezarte army who appears as a key figure in the conflict that sets the story of Maquia in motion. He is first seen leading a military expedition riding ancient flying creatures called Renato to invade the homeland of the Iorph, also known as the Clan of the Separated. His primary mission during this attack is to capture Iorph women by order of the king, who seeks their bloodline's longevity to secure the royal family's power. He is specifically responsible for the capture of a young Iorph woman named Leilia, an act that has lasting consequences for many characters.

In terms of personality, Isol is portrayed as a dutiful soldier rather than a man driven by personal malice or ambition. He carries out the king's command to invade the Iorph village and kidnap Leilia, but he does not appear to harbor any particular hatred for the Iorph people or seek to exploit their situation for his own gain. It is highly likely that he follows these orders simply because they are the commands of his royal sovereign. Evidence of his underlying discomfort with the nature of his mission can be seen later when royal officials, noting that Leilia's daughter Medmel shows no Iorph characteristics, suggest finding another Iorph woman for the prince to meet. At this suggestion, Isol frowns and listens as if he does not wish to hear what is being said.

Isol is also a capable and formidable warrior. When Krim, a young Iorph man who shares a close history with Leilia, comes to rescue her from the royal capital, Isol confronts and kills him. This act earns him Krim's deep hatred, yet Isol himself seems to view his actions as a duty that has left him with a heavy conscience. He later asks for a chance to atone for his sins, indicating a recognition of the wrongs that have been committed.

Isol's role in the story evolves from that of an enforcer of the kingdom's will to a figure who facilitates a degree of redemption. During a subsequent war between Mezarte and the neighboring kingdom of Bayer, Krim attempts to kill both himself and a captive Leilia in a murder-suicide. In this crucial moment, Isol intervenes, apparently saving Leilia and allowing her to go free so that she can meet her daughter, Medmel, under the circumstances. After this act, he returns to the battlefield to remain with his soldiers until the very end. Following the conclusion of the war, Isol watches as Leilia rides away on a Renato with captive soldiers tied up in tow. He states simply that he no longer needs Renato and no longer needs the Iorph. After this point, his ultimate fate and whereabouts are not depicted in the film.