They are composed of core components, which are the actual Circuits so to say, and bypasses that connect those components to the brain. Magic Circuits do not change and once damaged they cannot be repaired. Because organic activity is necessary for the operation of Circuits, it is a common mistake to think that they are literally a part of the magus body. There are rare occasions in which the Circuits continue working even after the practitioner’s body has ceased all vital functions. In these cases, destruction of the brain is necessary to stop the Circuits. Their Quality and Quantity are ranked through letters like Magecraft, and their Composition often varies between magi.