13 stands for change and reflects man's fear
of the unknown. In Tarot, the 13th card is death. 13 is unlucky though lucky to left-handed people. 13 is the ideal size of a coven. 13 are the number of stars that create the Jester constellation. There are 13 full moons during a year.
Superstition states that if 13 people meet in palaver 1 will die within a year. If you have 13 letters in your name you are said to have the Devil's Luck. Book of Shadows contains 13 letters.