Liza Quillyn is the headmistress of the College, an institution for magical education. An elderly woman with white hair, she is typically depicted wearing a scarf and shawl covering much of her upper body. Distinctive roses grow from her neck, signaling plant-based magical abilities, specifically plant cultivation.

Her tenure faced significant challenges, including internal opposition and external threats. She elevates the safety of students and staff above all, skillfully navigating political conflicts within the College while managing hostile external factions. This pragmatic approach manifests when she lowers the College's protective veil during a crisis involving Philomela Sargant, containing a dangerous magical artifact (The Testament of Carnamagos) but leaving Philomela vulnerable. She justifies this by emphasizing her duty to protect the broader institution, stating that risking everyone for one self-destructive individual is unacceptable.

Liza exhibits a complex dynamic with students. She initially welcomes Chise Hatori and Elias Ainsworth to the College, offering Chise a rose while advising caution despite the College's efforts to maintain safety. She observes Chise's potential, noting her timid exterior conceals inner resilience and predicting Chise will forge her own path. However, Liza later confronts Chise harshly when Chise insists on pursuing Philomela despite the risks. She grabs Chise by the scruff, points to her cursed black arm, and criticizes her "pathetic, self-congratulatory compassion," urging her to prioritize genuine safety over self-sacrificial impulses. This underscores Liza's belief in pragmatic survival over emotional idealism.

Her leadership philosophy centers on achieving maximum stability through minimal intervention, described as "attempting to achieve the most by doing the least." She faces criticism, such as from Gregory the vice-principal, for perceived inaction in investigating the missing magic book. Her rationale implies tactical patience, suggesting she allowed the book to reveal itself within the sealed College to control its threat.

Liza demonstrates profound knowledge of magical limits and dangers. She is visibly astonished witnessing Chise Hatori's transformation into a dragon and her subsequent travel through the earth's ley lines, recognizing the feat far exceeds ordinary mage capabilities. This event highlights her awareness of extraordinary power and its implications.