Episode Title:
Gold Transmutation (Ars Magna).
Episode Description:
Stiyl explains the dead knight was from the 13 Knights of the Roman Catholic Church and that a magical barrier is concealing all magical occurrences inside the school from the public. Tōma and Stiyl are forced to separate when the students, under the control of a spell, cast an imitation of a Gregorian choir to attack. When Stiyl destroys the spell's source, he finds Aureolus while Tōma runs into Aisa, who reveals that she came to Aureolus willingly because the Misawa Cram School is able to repel vampires, who are otherwise ordinary people. Aureolus had agreed to help her with her powers if she used her blood to lure vampires to the Misawa Cram School in order to save someone important to him. When Aureolus finds them, Aisa confronts him about his objectives and threatens to leave if he continues to kill people. However, Aureolus seals Tōma and Stiyl's memories, and the two awaken outside the school without any recollection of their mission until Tōma uses his Imagine Breaker to nullify the spell. Meanwhile, Index has followed Stiyl's mana trail to the school, but is put to sleep and captured by Aureolus. The remaining 13 Knights attack the school with a true version of a Gregorian choir, but it is restored by Aureolus's true power, Ars Magna. Tōma finds Sphinx outside with Index's habit and realizes that Index is now inside the school.
