Thaumaturgical bullets each containing a piece of one of Kiritsugu’s ribs, whose Origin is that of “sever” and “bind.” As “sever and bind” imply, the bullets impart an irreversible change on their target. When used on a magus, the target’s magic circuits are first severed into shreds, and then rebuilt with the connections all misplaced, rendering them useless. 66 bullets were made with core of bone shard from Kiritsugu’s 12th rib condensed using an esoteric spiritual process. He has already used 37 of the 66 bullets. That means there are 37 magi that are no longer in the world. Kayneth falls victim to the 38th bullet.