The great ghost hunter Carnaki often used an "electric pentagram" to protect himself from the forces unknown. Recently it has come up for sale at auction. It is still in usable shape if one replaces the old Victorian battery with a better energy source. Interestingly, it is reported that it interacts oddly with modern technology. Ghosts have a tendency to be thrown from the pentagram into any cell phone. The results are to say the least... interesting. Secret bids will be accepted before the actual auction.
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