Lye Batenkaitos was a short and youthful looking boy, standing at four feet and eleven inches tall, the same height as his younger brother. Despite his childlike appearance and high pitched voice, his body bore the marks of cruelty and violence. His dark brown hair with red tips hung unkempt down to his knees, covering his right eye, while his dark skin was covered in whip and bite scars. His thin frame was surprisingly muscular, and his piercing emerald green eyes and sharp fang like teeth gave him a sinister presence, often accentuated by his sadistic grin.

His outfit, unlike the standard Witch Cult attire, reflected his feral nature. He wore a tattered black cloak with red patterns over a tight purple bodysuit that exposed much of his upper body. Pink stripes ran across the suit, and his bare arms and feet were caked with grime. Strapped to his forearms were two Witch Cult daggers, his main weapons in combat.

In Arc 5, Lye revealed the full extent of his mutilated body, displaying numerous wounds and scars that made him appear inhuman. After using Solar Eclipse, his body transformed into a monstrous fusion of his victims’ parts, his limbs uneven, his head grotesquely misshapen, and fragments of those he devoured visibly merged into him. Unaware of his own hideous state, he embodied the horrifying essence of Gluttony itself.

Lye believed that life was about experiences, and that true power came from knowledge and memories. To him, knowledge was power, and memories were bonds—making his philosophy and existence the greatest. Because of this, he valued the quality of his meals, often testing his opponents to see if they were worthy before consuming them and gaining their abilities through the Authority of Gluttony, befitting his title as the Gourmet.

Unlike Roy, Lye believed that since the number of lives in the world was limited, so too was the number of worthy meals. He refused to waste an opportunity to eat someone valuable, disliking Roy’s indiscriminate approach to devouring anything. Though he occasionally showed concern for his sister Rui, mentioning she might be pleased if he ate Otto, Felt, or Dynas, he ultimately prioritized himself and would abandon her if threatened. His past with his siblings remained unclear, but he showed a notable dislike toward merchants.

Lye considered Subaru his “savior,” as Subaru could remember those whose names were eaten. He felt that the world’s forgetfulness robbed him of satisfaction, but Subaru’s remembrance gave his gluttony meaning. When confronting Ram in the Pleiades Watchtower, Lye tried to consume her, believing his hunger and desire were the purest forms of love. He directed this twisted affection toward her until his dying breath. Lye often spoke in a collective manner, using “us” and “we,” and when using Solar Eclipse to take the form of someone he had devoured, he mimicked their mannerisms and speech.

Lye Batenkaitos possessed the Authority of Gluttony, which allowed him to consume the names and memories of others, erasing their existence and claiming their experiences, talents, and skills as his own. By touching his target with his left hand and chanting their full name, he could devour their essence, storing it within the “Stomach of Souls” shared among his siblings. Victims who lost their names were forgotten by all, while those who lost their memories became hollow shells. Lye could also use Eclipse, the trump card of Gluttony, which came in two forms: Lunar Eclipse, allowing him to access the abilities of those he consumed, and Solar Eclipse, transforming his appearance into his victims. Initially fearful of losing himself through transformation, Lye eventually overcame this and freely used both forms, amplifying his combat abilities to monstrous levels.

Through the countless lives he devoured, Lye became a master combatant, inheriting numerous techniques and forms of magic. His abilities included devastating strikes like the Palm of the Fist King, teleportation through Leaper, and enhanced durability via Carnivorous Beast. He also wielded powerful magic, such as water barriers, ice-based attacks, and invisible wind blades. After consuming Emilia’s name, he gained access to her Ice Brand Arts, crafting ice weapons with deadly precision. Like his siblings, Lye could control witchbeasts and theoretically create life through his Witch Factor of Gluttony, though he never did. Armed with his Witch Cult daggers and his prophetic Gospel, Lye stood as one of the most formidable and sadistic Sin Archbishops in existence.

Much of Lye’s past remains a mystery, though Roy revealed that he, Lye, their birth parents, and their sister Rui all died shortly after birth. He also mentioned that their foster parents were unpleasant individuals, suggesting a harsh upbringing. The numerous scars covering Lye’s body further imply that his early life was filled with pain and brutality. Additionally, his deep resentment toward merchants hints at a troubled past involving them.

After he and his brother obtained the Authority of Gluttony and became Sin Archbishops, Lye eventually reunited with his sister Rui when she used Solar Eclipse to possess Roy’s body. It is implied that this ability worked both ways, as both brothers were fully aware of her existence and presence.