Some say the pentagram is mystical because 5 is mystical. It's a prime number, the sum of 2 and 3, as well as of 1 and 4. Christ had five wounds, they say, if you don't count those inflicted by the crown of thorns; and he distributed five loaves of bread to five thousand people. Most importantly, we have five fingers, toes and senses.

Some Christian watchdogs apparently think the pentagram is the devil's hoof print. They are especially on the lookout for inverted pentagrams as proof of Satanism, but any pentagram will suit most of these caretakers of decent symbology in their never-ending quest to identify evil. Of course, it can be bad for business if rumors are spread that one's company uses the pentagram or any other symbol deemed to be diabolical. Proctor and Gamble was once accused by Amway competitors of being run by devil worshippers who flaunted their satanic religion with a diabolical logo. The logo consisted of an old man's bearded face in the crescent moon, facing thirteen stars, all set within a circle. Some saw 666, the number of the Beast in Revelation (usually identified with Satan by the Christian watchdogs), lurking in the old man's beard and in the arrangement of the stars. Others saw a goat, surely a sign of the devil. A suit was filed against Amway but it was eventually thrown out of court.*

To the Wiccan, the five points of the pentagram represent Air, Fire, Water, Earth and Spirit. Wiccans usually put the symbol in a circle, which has traditionally represented the endless or eternity. The ancient Chinese believed there were five elements (wood, fire, earth, metal, and water), five planets, five seasons, five senses, as well as five basic colors, sounds and tastes. However, the number six seems to have been more enchanting to them than five, for the I Ching uses six as its base number. So does the Star of David, which has six points and is made by overlapping two equilateral triangles. The Star of David is a hexagram but is not used to cast a hex on you.  That kind of hex comes from the German word for witch, Hexen, which is related to the Old High German word hagzissa, a hag.
Occultists of all sorts wear pentagram talismans to protect them from evil or to help them get occult knowledge and power. They even draw pentagrams on the ground and stand within them to better call upon occult powers. If the point is aimed north, they are not worshippers of Satan. However, if the point is aimed south, they are. So say the Christian watchdogs.

For some reason, the pentagram has become the symbol for a star, though no star in the sky looks like a pentagram, unless perhaps it is seen from inside the five corners of the earth when one is five sheets to the wind. Furthermore, some mystics claim that if one stares at a small pentangle long enough one will see that all triangles end in a circle with five sides.

.The Pentagram signifies the domination of the mind over the elements, and the demons of air, the spirits of fire, the phantoms of water and ghosts of earth are enchained by this sign. Equipped therewith, and suitably disposed, you may behold the infinite through the medium of that faculty which is like the soul’s eye, and you will be ministered unto by legions of angels and hosts of fiends."

Going deeper yet, the upside-down star/pentagram has long been recognized as the symbol of Satan. Anton LaVey, author of the Satanic Bible and The Satanic Rituals, lavishly used this symbol in his ceremonies and rituals–most often depicted as the "goat’s head."

Rev 13:16 And he causeth all, both small and great, rich and poor, free and bond, to receive a mark in their right hand, or in their foreheads:
Rev 13:17 And that no man might buy or sell, save he that had the mark, or the name of the beast, or the number of his name.
Rev 13:18 Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of a man; and his number is Six hundred threescore and six.