Seal of Solomon

The primary inspiration for the franchise would be the not so ancient grimoires : medieval manuscripts that details the art of magic, particularly the Grimorium Verum and Lesser Key Of Solomon. These books detail the summoning of spirits in accordance to the cardinal four elements : fire, wind, water and earth. This is accomplished with various magical seals, but the primary seal and core of the practice is the Seal of Solomon.

This is a symbol said to have been on a ring possessed by Solomon, which he used to control spirits to do his bidding and speak to animals. It is a hexagram caught in a circle.