Teresa was the strongest Claymore of her generation and possibly the most powerful one of all time.. She was famously known as Teresa of the Faint Smile for effortlessly slaying enemies with a faint smile on her face. She is so powerful that she rarely use more than 10% of her Yoki in battle. Her rise to Claymore No. 1 leads to the demotion of the previous No. 1, Rosemary, who, angered by Teresa's promotion, challenges her to a duel as an Awakened Being. Not long into the fight, Teresa dispatches her easily by releasing only a little of her Yoma energy.