Therese Alexandrite serves as a combat mage within the Vassal Weapon Heroes, guardians shielding their realm from interdimensional incursions. Her gemstone-based sorcery channels elemental forces through refined jewels, amplifying her capabilities. Accessories forged by Naofumi temporarily elevate her magic to levels comparable to a Legendary Hero’s strength. Her "Shining Stone" arsenal spans destructive flames, searing lightning, and celestial meteor showers alongside strategic tools—paralyzing crystal butterflies, hypnotic smoke veils, and shimmering barriers. She seamlessly integrates spells with allies’ combat styles: electrifying L'Arc’s scythe swings, entwining blizzards with Glass’ techniques, or masking her group’s identities through intricate illusions. First encountered as an adversary allied with L'Arc and Glass, she pursues their mission to dismantle Melromarc to preserve their homeland. Yet her magic consistently spares allies, revealing an undercurrent of empathy. Confronted by transcendent dangers like Kyo Ethnina, she shifts into a provisional partnership with Naofumi’s faction, prioritizing mutual survival over entrenched rivalries. While her strategies adapt to apocalyptic threats, her core allegiance stays anchored to her original comrades and cause. No records detail her origins or life beyond battlefield engagements. Her journey emphasizes the gray interplay between obligation and conscience, casting her alternately as opposition and collaborator as cataclysms demand fluid alliances.