The protective circle used to trap Meg in 1.22 Devil's Trap contains a heptagram (also known as a septagram, septacle, or seal of Babylon), with a hexagon and two circles. The scorpion in the center is the fifth pentacle of Mars, about which the Key of Solomon says: Write thou this pentacle upon virgin parchment or paper, because it is terrible unto the demons, and at its sight and aspect they will obey thee, for they cannot resist its presence.
The design as a whole forms the Great Pentacle: It should be written on sheepskin paper or virgin parchment, the which paper should be tinted green. The circle with the 72 divine letters should be red or the letters may be gold. The letters within the pentacle should be the same red, or sky blue everywhere, with the great name of God in gold. It serves to convene all spirits; when shown to them they will bow and obey you.
A heptagram is a seven-pointed star drawn in one continuous line, in the manner of the five-pointed pentagram. It can be found in the holy seal of the Brotherhood of the Silver Star, and its history as a protective design has led to the the seven-sided shape of most sheriff's badges.
The heptagram is also found in Western kabbalah, where it can be a symbol of the seven notes of music, the seven colors of a rainbow, the seven planets, the seven alchemical metals, the seven days of the week, and the sphere of Netzach.