A Demon Sword of Thunder who can shape-shift to human form. In her human form, she is a quiet, sad girl. Elsa was born from the rage of the Old Knight when his daughter was slain. She has the same name as his daughter.
After his defeat, she slays him with a misericorde, fulfilling the promise made by his real daughter and dying herself from the wounds she received fighting Cecily and Aria. She transforms into a sword by chanting "Shake off your slumber. The time is at hand. By the judgement of thunder, kill God" (眠りを解け。時は来たれり。雷の裁きを。-神を殺せ?).