The seal of the wizard King Solomon. It is supposed to be able to raise evil sprits: see how to summon the devil.

               +--------------+
               |              |
               |              |
               +----+    +----+
               _    |    |    _
               |    |    |    |
    +----+  |--+--| |    | |--+--|  +----+
    |    |     |    |    |    |     |    |
    |    |     ¯    |    |    ¯     |    |
    |    +----------+    +----------+    |
    |                                    |
    |    +----------+    +----------+    |
    |    |     _    |    |    _     |    |
    |    |     |    |    |    |     |    |
    +----+  |--+--| |    | |--+--|  +----+
               |    |    |    |
               ¯    |    |    ¯
               +----+    +----+
               |              |
               |              |
               +--------------+
This is supposed to be a close approximation, but my ASCII art ain't that good.