Naberius Kalego serves as a prestigious professor and homeroom teacher of the Abnormal Class at Babyls Demon School. Born into the Naberius clan, known as loyal guard dogs, his path as the second son was predetermined to become Babyls' watchdog. A prodigy, he achieved Rank 4 (Daleth) upon starting his first year. His school years were marked by a desire for solitude, frequently disrupted by conflicts instigated by the delinquent top dog, his upperclassman Opera. During this time, he forged a lasting friendship with the high-ranking demon Balam Shichiro. Kalego's class won the Music Festival during his first year, demonstrating his early leadership and musical talent. He later became a teacher under the mentorship of Dantalion Dali, solidifying his dual role as educator and guardian. Kalego possesses a tall, lean frame with short, deep purple hair styled in a side-swept wing. He typically wears a long purple cloak under a shoulder capulet with white trimming, a studded purple belt, and the traditional Babyls teacher's uniform. His black fingernails and habitual scowl enhance his intimidating presence. As a student, he wore a modified purple Babyls uniform and had longer hair with bangs. When summoned as a familiar by Iruma Suzuki—a consequence of Iruma's human nature—Kalego transforms into a small, owl-like creature with bat-like wings, horn-like tufts, and his signature front hair curl, roughly the size of a grapefruit. His personality is stern, antagonistic, and short-tempered. He frequently demands silence ("Shukuni") and displays pessimism toward students, rarely offering praise. He detests boisterous or inconsiderate individuals, immediately disliking troublemakers like Clara and initially resenting the Abnormal Class. Intimidating and sadistic toward those he dislikes, he vents frustrations through punitive measures like assigning extra homework. Despite this, he adheres strictly to principles: he never punishes unjustly, acknowledges student achievements fairly, and honors promises, such as permitting the Abnormal Class to use Royal One. He maintains integrity as an educator, privately documenting each student's strengths, weaknesses, and progress in detailed notebooks and providing tailored feedback during home visits. Though masking concern with severity, he genuinely cares for his students' safety and growth, designing rigorous trials to unlock their potential. He collects cacti, possesses musical proficiency playing nearly all instruments, and suppresses lighthearted emotions like laughter. He shares a unique, respectful friendship with Balam, unaffected by others' fear of Balam's appearance, yet remains easily cowed by Opera, his former tormentor. Kalego's story reveals evolving dynamics, particularly with Iruma. He initially resents Iruma for summoning him as a familiar, causing public scenes, and being Sullivan's grandson. Yet, he expresses concern for Iruma's safety, urging him to rely on adults and appearing perplexed when Iruma avoids summoning him during crises. Over time, Kalego acknowledges Iruma's resilience and academic progress, trusting him to persuade Purson Soi to join the Music Festival and reassuring him after canceling their familiar contract. After the Deviculum arc, Kalego learns Iruma is human but continues to protect him, prioritizing his role as teacher over species differences. His relationship with the Abnormal Class matures from mutual friction to guarded loyalty; he joins their group chat and intervenes decisively during crises, such as reaching Iruma first after the latter's underground ordeal in the Harvest Festival. Kalego also faces familial conflict with his brother Narnia, whom he once respected. After Narnia's actions endanger students, Kalego denounces him as an enemy of Babyls. As a Rank 8 (Cheth) demon, Kalego wields formidable magic. His abilities include instantaneously conjuring barriers to disrupt obstacles or attacks, generating electricity during attacks or emotional distress, and manifesting items like books or chairs via finger snaps. His bloodline magic, Cerberion, summons a sentient, three-headed demon beast crackling with electricity, capable of massive destruction; Kalego can manifest individual heads separately. Cerberion's overprotectiveness prevents Kalego from contracting other familiars, as it destroys them. When summoned by Iruma, Cerberion's form weakens to a puppy-sized creature, reducing combat efficacy but retaining utility. Kalego possesses broad magical knowledge, including spells like *La Fire* for fire creation, *Cherusil* for transfiguration, and *Gran* for barrier defense. His relationships further define his role. Opera remains a source of school trauma due to relentless provocations, leading to Kalego's ongoing avoidance and submission. He despises Lord Sullivan's brashness and humiliation tactics but earns Sullivan's trust as interim headmaster during emergencies. Kalego dislikes Bars Robin's teaching philosophy yet respects his archery skills, assigning him as Iruma's tutor. After severing ties with his brother Narnia following student endangerment, Kalego views him solely as an enemy. Momonoki Morax's unrequited crush contrasts his professional detachment, though she finds his familiar form endearing. Kalego's namesake echoes demonology: Naberius (or Cerberus), a Marquis of Hell depicted as a three-headed dog or raven, associated with rhetoric and restoring lost honors.