Agatha's might
As Claire's body was slowly freezing in ice, Estella pulled the string along with the energy arrow between her fingertips. She let out a smirk, "since you are a tenth-grade student and also from a great background, you probably had heard about the advanced attributes which actually form because of two basic attributes. What you are now seeing the example of it."
Claire frowned upon listening to her explanation. She remembered the two arrows Estella shoot at the sky, a while ago. "Wind and Water?"
Claire naturally had the knowledge of the advanced attributes. Even a grade-5 student in the academy knows of it as it was in the syllabus. However, she was sure that one cannot merge two attributes and create an advanced attribute directly. They should have awakened an Arcana spirit with the advanced attribute in the first place, then, those special talented Arcana masters will be able to use the two attributes with ease just like the twin and set Arcana users.