The Devil item known as the Rosary of Judgment that has the power to erect sealing spells & barriers/prisons, also used for the school's barrier. However, it can only be used for magic if one has some experience in doing so. It is owned by Tenmei Mikogami, Yōkai Academy's Headmaster.
However, it briefly fell into the hands of Hokuto Kaneshiro in his plot to reveal the existence of monsters to humans and start a war. After the Great Barrier was repaired, the Headmaster had it returned to him.