Demonic spirits like angles, and angelic spirits like circles. So this demon trap starts off as an angular square then deceives the spirit into the decreasing spiraling circle. The demonic spirit can only go counterclockwise inwards, but cannot come out clockwise, so it is trapped. The cross at the mouth snaps shut like a Venus flytrap with the phurba arrow pointed in. The original design is from a Hebrew spirit trap which was inscribed into a clay bowl to trap Lilith in her form as killer of children in utero and newly born.