Avaritia is a central antagonist from the anime 11eyes, serving as the leader of the enigmatic group known as the Black Knights. His name is derived from the Latin word for greed, aligning him with one of the seven deadly sins. Before his transformation into a Black Knight, his true identity was Georgius of the Rainbow, a highly respected and powerful magus belonging to the Index, a major magical organization. He was one of the Fourteen Saints of the Index, holding a position of great authority and strength, and was known for his legendary feat of defeating the evil dragon Crow Cruach that once terrorized London.

The character's personality is defined by an unwavering determination and a profound sense of duty. As the leader of the Black Knights, he is utterly committed to completing his mission, regardless of the personal cost. This dedication is so absolute that he is willing to sacrifice himself, his subordinates, or his own humanity to achieve his goals. While he appears cold and stoic, often remaining inactive and observing from his throne within the Crystal Palace, he is not without a sense of honor or care for his comrades, especially Superbia, his most trusted companion. His demeanor is typically calm and collected, with a voice that can be described as cold and determined, though the anime adaptation gives him a softer, more bored tone until the final conflict. A deep-seated hatred drives him, aimed both at the witch Liselotte Werckmeister and the malevolent dragon whose curse he carries within his own body.

Avaritia's primary motivation is to prevent the catastrophic return of the powerful witch Liselotte Werckmeister. Over sixty years before the main events of the story, he was dispatched with his subordinates to stop her. In a desperate battle, he used a forbidden technique known as the Contract of the Rainbow to shatter Liselotte's soul and her source of power, the Void Stone, into seven fragments. This act successfully sealed her within a large crystal, but the cost was immense. To maintain the seal eternally within a dimension called the Red Night, Avaritia and his fallen subordinates gave up their human forms, their souls bound to constructs of dark spirits called Larva by the onmyoji Misao Kusakabe, who became the Black Knight Superbia. Thus, his role in the story is that of a warden and an executioner. He refers to the protagonists as Fragments because their bodies unknowingly house the scattered pieces of Liselotte's power. For decades, his mission was to ensure these Fragments were eliminated to prevent the witch's revival, a task he oversees from the shadows.

Within the narrative, Avaritia is the commander of the Black Knights, which include Gula, Ira, Invidia, Acedia, and the crucial Superbia. His most significant relationship is with Superbia, who was once the onmyoji Misao Kusakabe. She is the one who bound his soul to his current form, and it is revealed that she has harbored deep feelings of love for him for over fifty years. While Avaritia's personal feelings toward her are less explicitly stated, he demonstrates immense trust in her, and she is his most loyal and reliable ally, often the only one who remains by his side until the end. His relationship with his other subordinates is more formal, as a commander focused on the mission. He shows a degree of respect for his best friend Gula and shares a unique connection with Shiori Momono, as they both hail from the same lineage of powerful magicians, the Bookshelf family, which ultimately makes them enemies.

Throughout the series, Avaritia remains a mostly passive figure, acting as the final guardian of the seal. He sends other Black Knights to fight the protagonists while he stays behind to maintain Liselotte's prison, a task that consumes much of his power. His development is reserved for the climax. When the seal is finally broken and Liselotte is freed, Avaritia is forced into direct combat. In a final act of desperation to destroy both the Fragments and the witch, he releases the seal on the dragon within him, transforming into the monstrous black dragon Crow Cruach. This act consumes his consciousness, and the dragon fights with immense power. Ultimately, his physical form is destroyed in battle. In a final, selfless act, his lingering will intervenes to help Kakeru Satsuki permanently seal Liselotte, grabbing her and allowing them both to be pulled into a void dimension, where they are trapped forever. A comedic alternate version of Avaritia appears in the 11eyes OVA, a parody episode where he is depicted as a masochist who is tied up and whipped by Liselotte, serving as her slave.

Avaritia possesses formidable magical abilities befitting a former Saint of the Index. His most powerful technique is the Contract of the Rainbow, a forbidden spell that manifests as seven-colored rays capable of tearing through powerful magical defenses. The true terror of this ability is that it does not simply destroy the target but denies its very source of existence, splitting its soul across seven parallel dimensions. He used this spell to defeat the evil dragon Crow Cruach and to seal Liselotte. However, the dragon cursed him with its dying breath, placing a fragment of its spirit within his body. As a result, Avaritia is forced to use a significant portion of his power to keep this dragon sealed, preventing him from fighting at full strength for most of the series. In his final confrontation, he releases this seal and transforms into Crow Cruach, which is even more powerful than in its original life, as it is further empowered by the dark spirits of the Red Night and can still use Avaritia's own Contract of the Rainbow technique. In his humanoid Black Knight form, he is also capable of high-speed chanting, creating powerful barriers, and firing intense energy blasts.