the thrax logo is not a pentagram- it is an 'inverted' pentagram. maybe they just inverted it in order to fit the A into the logo. notice the A would fit with a normal pentagram.
i still don't see the significance behind it them using it, though.
just got this info about pentagrams if anyone is interested:...
The right-side-up pentagram has been used by various Pagan religions for thousands of years. The inverted pentagram had been used by "old-school" medieval Satanists in their ceremonies that were simply the reverse of Christianity and a rebellion against it. Such pentagram was a magical symbol, as opposed to a religious symbol, like the inverted cross. During the 19th century, the magician Eliphas Levi, apparently, became the first person to "officially" distinguish the inverted pentagram as the symbol of "evil" (of medieval Satanism). The bottom point of the inverted pentagram pointed down, i.e. to "hell", or was a representation of winter (as opposed to that of a "regular" pentagram which represented "summer"). The inverted pentagram, often contains the image of the Baphomet, or the goat - the horned "god". Much later, Anton LaVey made the Baphomet the "official" symbol of the Church of Satan.
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To invert the figure is considered by some as a sign of relegating Spirit to the bottom of the metaphysical heap. Others take inversion to be Satanic and on par with alleged mockeries such as inverting the cross or saying the Mass backwards. Still others find nothing particularly diabolical about inversion and use the inverted pentagram without fear of accidentally invoking the forces of evil