Grer Gulliver is one of the four Gulliver brothers, who serve as high-ranking executives within the Freya Familia. He and his siblings, Alfrigg, Dvalinn, and Berling, are all Pallums and are known collectively as one of the most formidable units in the city of Orario. The four brothers are reincarnations of legendary figures from Norse mythology. In terms of appearance, the brothers are identical and always wear sand-colored armor with full-face helmets, making them indistinguishable from one another at a glance. The only reliable way to tell them apart is by the color of their eyes. Grer is identified by his red eyes, and he also wears long pieces of cloth matching this color attached to his armor. He is the youngest of the four siblings.

The personality of Grer Gulliver is deeply intertwined with those of his brothers, with whom he shares an exceptionally strong bond. The Gulliver brothers are defined above all by their absolute and fanatical loyalty to their goddess, Freya. This devotion overshadows all other aspects of their lives, as they desire her love exclusively for themselves. Consequently, they are hostile and antagonistic toward other members of the Freya Familia, viewing them as rivals and obstacles. The four brothers operate almost as a single entity, capable of communicating their will to one another without speaking and coordinating their actions as if they share one mind. Despite this seamless unity, they dislike being treated as interchangeable and have made efforts to establish their own individual identities, though with little success. Grer shares in the brothers’ collective pride in being among the strongest of their race, and they are said to be quite arrogant, even by Pallum standards.

The story behind their loyalty to Freya is central to their motivation. Before becoming adventurers, the brothers were master craftsmen and jewelers, famous for their skill. When Freya visited their workshop and commissioned a necklace from them, their Dwarf employer demanded a terrible price from the goddess in exchange for releasing them from his service. Upon learning that Freya had agreed to this sacrifice on their behalf, the brothers killed the Dwarf in a fit of homicidal rage and swore their eternal allegiance to her. This event forged their unshakeable resolve to protect Freya from any harm or indignity, and they strive to ensure she remains untouchable. They are also shown to be jealous of Bell Cranel due to the intense personal attention he receives from Freya, though after training with him, they develop a grudging degree of respect for his abilities as a warrior.

As an executive of the Freya Familia, Grer plays a significant role as a first-class combatant in the city's power struggles. He and his brothers are a major force during the conflict against the Freya Familia, where their exceptional teamwork and individual prowess make them incredibly dangerous opponents. Their reputation is such that their combat synchronization is said to be the best in the city, allowing them to challenge even higher-level adventurers when they fight together. However, their effectiveness is severely reduced if they are separated.

Regarding his key relationships, Grer is bound most closely to his three brothers. Though they work in perfect harmony, their dynamic is not without hierarchy. Their eldest brother, Alfrigg, believes it is his duty to keep the others in line, though they typically ignore his authority. Despite not respecting him as a leader, all the brothers, including Grer, are said to harbor an intense fear of Alfrigg's terrifying wrath when he is finally provoked. Outside of the family, the brothers maintain a relationship of mutual hatred with most of their Familia allies like Allen Fromel and Hedin Selland. They also have a known disdain for Finn Deimne, another famous Pallum, expressing a preference for working with the dwarf Gareth Landrock instead.

Grer does not undergo a significant personality transformation, but his role in the story does show a slight evolution in his perspective. Initially viewing Bell Cranel merely as an object of Freya's unwanted affection, the Gulliver brothers’ repeated interactions with him, including training sessions, lead them to acknowledge his strength and determination, ultimately respecting him as a true warrior rather than a nuisance.

The combat abilities of the Gulliver brothers are formidable, as all four are established as Level 5 adventurers. Their physical prowess is massively superior to that of lower-level individuals, granting them incredible strength, speed, agility, and durability. Their teamwork is their greatest weapon. They can move in perfect sync, allowing them to perform assaults that produce shockwaves and overwhelm forces of thousands. In addition to their collective power, each brother excels in a specific analytical role. Grer's unique talent is his incredible observation skill. In the midst of battle, he is able to pick up on an opponent's habits, abilities, and subtle weaknesses, relaying this crucial information to his brothers to inform their strategy. In terms of equipment, Grer wields a large greatsword, which is oversized for his stature, using it with devastating efficiency. His past life as a master artisan also makes him highly proficient in the maintenance of weapons and equipment.