Halley Astry, a 29-year-old human male born in 1824, serves as a homeroom professor at the Alzano Imperial Magic Academy. A Quinde (Rank 5) mage aligned with the Alzano Empire, he instructs Class 1 and frequently clashes with colleague Glenn Radars, openly criticizing his informal credentials and unconventional teaching style. Despite his abrasive exterior, Halley prioritizes the academy’s security, taking decisive action during crises like the "Fejite’s Worst Three Days."

He possesses light brown hair, black eyes, and dons the standard instructor uniform, though alternate depictions present him with blonde hair tied in a ponytail and yellow eyes—variations attributed to adaptation-specific designs. His personality merges sharp criticism with steadfast loyalty, persistently highlighting Glenn’s flaws while defending the institution’s protocols.

Halley’s early history remains obscure, though records note his rise within the academy’s faculty as a rival to Celica Arfonia. Media portrayals diverge slightly: light novels and manga show him frustrated by a student’s premature loss in a competition, while the anime frames him as anticipating the outcome, underscoring a strategic, composed demeanor.

His interactions remain consistent across adaptations, maintaining contentious dynamics with Glenn and a competitive tension with Celica. Though spin-offs and ancillary media lack elaboration on his development, his actions consistently balance skepticism with a principled dedication to the academy’s stability.