The As Above, So Below Granny Square is available on my YouTube Channel for free. So, if you are purchasing this pattern I really appreciate your support!
Recommended yarn is Worsted Weight with a 4mm hook. You will need 12 Stitch Markers and 2 colors of yarn minimum. My squares come out to approximately 5 1/2 x 5 1/2 inches. Size varies depending on materials and tension.
The symbol is called a unicursal hexagram, which is a 6 pointed star made in a continuous line. Great for fans of Supernatural (see Supernatural: Men of Letters).