Ais Wallenstein, the Sword Princess, is a first-class adventurer and executive of the Loki Familia. Her life was marked by childhood trauma when the One-Eyed Black Dragon killed her parents, fueling a lifelong quest for vengeance through strength. She joined the Loki Familia at age seven. Her mother, Aria, was a spirit, and her father a dungeon hero, leaving the nature of her birth unexplained. Initially volatile and self-destructive, she earned the moniker "Doll Princess" for her lifeless eyes and fragile demeanor. She recklessly disregarded her own well-being, defied authority, and fixated solely on physical power, hurling herself into lethal situations like battling Infant Dragons alone while still Level 1. Mentorship from Loki Familia executives—Finn Deimne, Riveria Ljos Alf, and Gareth Landrock—gradually instilled mental resilience, technical combat skill, and the value of rest. Finn focused on fortitude and strategy, Riveria on magic and academics, and Gareth on balancing training with recovery. Despite this growth, her core hatred for monsters and obsession with power persist, often triggered by using her Avenger skill or reminders of the Black Dragon. Her combat prowess is exceptional, specializing in monster slaying. She achieved Level 2 within her first year, setting a record later surpassed by Bell Cranel. She leveled rapidly, reaching Level 6 after single-handedly defeating the floor boss Udaeus. Her signature wind magic, Ariel, grants three-dimensional movement and physical enhancement, allowing her to challenge stronger foes. The Avenger skill amplifies her attack power against monsters, especially dragon-types, fueled by hatred, but clouds her judgment, reverting her to a feral state. Her duel prowess against humanoids remains comparatively unrefined, as noted by adversaries like Ottar. Ais is typically reserved, struggling to express emotions verbally, leading others to perceive her as enigmatic or aloof. Naivety and gullibility stem from her single-minded focus; she believed Loki's false claims that shouting technique names increased their power or that revealing combat clothes were practical. A traumatic punishment by Riveria at age seven—binding her to adamantite weights and throwing her into water—left her unable to swim and terrified of deep water, which she avoids even in the Dungeon. Her relationship with Bell Cranel proves pivotal. After saving him from a minotaur, she becomes fascinated by his rapid growth and contrasting purity. She secretly trains him, and their interactions evoke unfamiliar emotions like happiness and jealousy. She reacts with startling possessiveness towards other women near Bell and punishes him with forced lap pillows upon discovering his additional trainers. During the Xenos incident, she clashes with Bell over protecting the monster girl Wiene but later reconsiders her stance after witnessing Wiene's empathy. This encounter, combined with training under Ottar, leads her to conclude monsters can possess human hearts and people can harbor monstrous ones, vowing to judge individually who constitutes a monster. Within the Loki Familia, Riveria acts as a mother figure, guiding Ais since childhood and understanding her emotional struggles deeply. Loki frequently teases her with perverse antics but holds genuine care. Ais shares bonds with Lefiya Viridis, whom she reluctantly trains, and the Hiryute sisters, with Tiona aiding her socialization. Her past remains a closely guarded secret shared only with Loki and the top executives; even Riveria is excluded after traumatic events like her defeat by Revis, who referenced her as "Aria." Her development shows a shift from isolated vengeance towards a nuanced understanding. While still driven to defeat the One-Eyed Black Dragon, her experiences with Bell and the Xenos challenge her black-and-white worldview, allowing her to acknowledge shades of morality in both monsters and people.