Halley Astry, a 29-year-old human male born in 1824, serves as the homeroom professor for Class 1 at the Alzano Imperial Magic Academy, holding the Quinde mage rank (Rank 5) within the empire’s hierarchy. His appearance features light brown hair—alternately depicted as ochre or blonde in adaptations—and black eyes, though some sources describe them as brown or yellow. He adheres to the academy’s standard instructor uniform.

Appointed directly to the faculty, Halley oversees Class 1 while harboring a professional rivalry with Celica Arfonia and frequent clashes with Glenn Radars, a fellow instructor whose unconventional methods and lack of formal credentials challenge Halley’s emphasis on structured pedagogy. Despite his stern critiques of Glenn, Halley prioritizes institutional integrity, actively defending the academy during crises like the "Fejite’s Worst Three Days."

Adaptations diverge slightly in his portrayal: light novels and manga depict him voicing disappointment when a student underperforms in the Spirit Defence event, whereas the anime shows him anticipating the same student’s swift defeat. His criticisms of Glenn often center on practical adherence to professional standards, yet his actions consistently underscore a deeper loyalty to the academy’s mission and student welfare. No expanded backstory or character arcs are detailed in existing narratives.