Grim is a mysterious and highly skilled Hunter sorcerer who joins the main protagonists on their quest. He is a tall, lean man whose most defining physical characteristic is being wrapped from head to toe in white, feathery bandages. These bandages, made from the feathers of a special tree, possess notable healing properties for both himself and others. On the part covering his face, there are drawn-on pointy teeth over the mouth area and what appear to be red glasses or transparent red material over his eyes. He wears a black, pointed hat with a feather, a flowing black cloak, and black pants with white shoes. His white gloves feature a drawn symbol, and he carries a belt where he stores scrolls containing his weapons.

Very little is known about Grim's past or where he originally came from, contributing to his enigmatic nature. His personality is notably calm, reserved, and serious, often preferring to work alone. He possesses excellent battle instincts whether he is fighting a Nemesis or another sorcerer. One of his most distinctive behavioral traits is that he always speaks in the third person and maintains a polite manner of speaking. He also has a habit of testing people he fights, trying to determine if they are truly his enemy. Perhaps his most unusual and pronounced quirk is a powerful fear and anxiety triggered by the sight of blood. This reaction is so intense that he will stop whatever he is doing to treat his wounds and has even been observed storing his own blood in small jars.

Grim's path crosses with the main protagonist, Seth, in the town of Rumble Town, beginning with a misunderstanding where Grim initially mistakes Seth for an enemy and attacks him. After this conflict is resolved, Grim aids Seth in defending the town and heals a wounded arm using his magical bandages. Following the defeat of the local antagonist Hameline, the Inquisition arrives, and Grim helps Seth and his companions escape. Having grown fond of Seth, Grim decides to join him on his journey to find the mythical Radiant.

As a Hunter sorcerer, Grim is highly proficient in combat. When channeling Fantasia, the magical energy of his world, the energy he produces is a distinctive dark blue. Many of his spells have musical or Latin-inspired names. Among his known abilities is the spell Procella, which fires a beam of blue flame-like energy that can push a target back. Veneticium Revelare allows him to channel Fantasia into his glove and spin like a small tornado, releasing slashing energy waves in all directions; he can also use the glove to see distant locations. Caeca Nube enables him to send a ball of Fantasia toward an enemy that he can detonate on command, effectively creating a smokescreen. Additionally, the bandages covering his body can reflect attacks or seal and absorb objects, releasing them back out later.