Orsola Aquinas

 Orsola Aquinas (オルソラ＝アクィナス) is a Roman Catholic nun.

Appearance
She initially wears a black nun's robe from her days back in the Roman Catholic Church, but as of Volume 16, her attire changes to a plain white nun's robe of the English Anglican Church. She has a unique way of talking; according to Touma, her way of thinking resembles that of a grandmother. She often ends up talking about something unrelated before jumping back to the original topic, often leaving people flabbergasted. In Volume 11, she states that her hometown is in Chioggia, Italy.

Plot
Book of Law Arc

A former decoder of grimoires and other magical texts, she is allegedly able to decode "The Book of the Law", a powerful Roman Catholic Church grimoire. Because of this, she is captured along with The Book of the Law by the Amakusa Catholics. The Roman Catholic church sends the Anieze Forces to save her, while Necessarius sends Stiyl, who drags Index and Touma with him.

It is later revealed the the Amakusa Catholics were actually trying to save Orsola, and that the Anieze Forces were sent to dispose of her because the Roman Catholic Church labeled her as dangerous due to her being able to decode The Book of the Law. She is saved by Touma and company, and becomes a decoder for the Anglican Church. She works alongside Sherry Cromwell, and the two of them get along somehow.