Arystor Krory, often referred to as Arystar Krory III, is an Exorcist affiliated with the European Branch of the Black Order. He is a tall, lean man of Romanian nationality with sharp facial features, pointed ears, and short black hair distinguished by a prominent white streak. As a baron by birth, he spent the majority of his early life isolated within his late grandfather's castle. The combination of his family's reclusive nature and the aggressive carnivorous plants his grandfather cultivated led the people of the nearby village to fear him, believing him to be a vampire.

Krory's personality is marked by a stark duality. In his daily life, he is extremely naive and sensitive due to his sheltered upbringing, often leading to comical misunderstandings or emotional outbursts, such as crying over minor incidents. He is a poor judge of character and is easily deceived, which sometimes makes him feel like a burden to his comrades. However, when his Innocence activates in combat, he transforms into a violent and feral berserker, driven by a bloodthirsty instinct to destroy Akuma. Despite this savage state, he retains enough awareness to never intentionally harm his allies.

His path to becoming an Exorcist was tragic and born of deception. After his grandfather's death, he was left with a deep sense of purposelessness, praying for something he could call his own. It was during this time that a stranger, later revealed to be General Cross Marian, returned one of his grandfather's plants, a carnivorous specimen named Roseanne. When the plant bit him, Krory experienced agonizing pain before his teeth fell out and were replaced by a parasitic form of Innocence. Unaware of the nature of his power, his body instinctively began hunting Akuma, which he mistook for attacking humans. On one such hunt, he encountered a beautiful woman named Eliade. He fell deeply in love with her, unaware that she was a Level 2 Akuma. Eliade, who genuinely returned his affections, manipulated him into believing he was a true vampire to keep him isolated in the castle with her.

This isolated existence ended when Exorcists Allen Walker and Lavi were summoned to the village to destroy the "vampire." During the ensuing battle, Allen's cursed eye evolved, revealing Eliade's true soul and forcing Krory to confront the reality of her nature. Heartbroken, Krory was compelled to destroy her. Overwhelmed with grief and believing he had no right to live after killing his love, he attempted to end his life using his grandfather's carnivorous plants. It was Allen Walker who convinced him to live, arguing that Eliade's death would be meaningless if Krory threw his own life away. Seeking a reason to exist and a purpose for his power, Krory joined the Black Order as an Exorcist.

Within the story, Krory serves as a powerful close-combat fighter. His primary motivation shifts from finding a reason to live to protecting his new-found family within the Order. He shares a significant bond with Allen Walker, who saved him from his despair and gave him a second chance. He also develops strong, protective relationships with his other comrades, such as Lavi and Lenalee, though his naivety often makes him the target of their exasperation. Over the course of the series, Krory gradually emerges from his profound depression. While he remains sentimental and still struggles with his self-worth, he learns to trust his allies and accept his role as an Exorcist, moving past the tragedy of Eliade to find a new sense of belonging.

As a Parasitic type Accommodator, Krory's unnamed Innocence manifests as a set of sharp fangs that grant him unique abilities centered on blood. These fangs act as an Akuma sensor, allowing him to instinctively detect his enemies. His primary ability allows him to drink Akuma blood without being infected by the Akuma virus, which temporarily grants him enhanced speed, immense durability, and superhuman strength sufficient to crush an Akuma's armor or stop a direct blow from Lavi's hammer. He can also manipulate his own blood for offensive purposes. By injecting his Innocence-laced blood into an Akuma, it acts as a potent poison that causes the target to explode. He can also fortify his fists with hardened blood to increase his destructive power. When pushed to his absolute limits, Krory can drain the blood from his own body to create Bloody Krory, a powerful, winged blood mannequin he can control remotely as an almost invulnerable avatar. He can also use his ability to suck the Akuma virus out of an infected ally, though this leaves him completely exhausted.