Captain Blackthorn grimaced against the salt air that sandblasted his face. His men were weary, his ship was falling apart and the hold was replete with treasures beyond counting. It was time to head home and enjoy the bounty that years at sea had brought them. As he braced himself against the pressing squall he considered the conundrum of converting said bounty into a transferable asset that could easily be spent without arousing suspicion of the local militia or the jealousy of rival pirates. If only large amounts of wealth could be represented on something as light and unobtrusive as a piece of paper. But then Blackthorn had a idea:
"I know what we'll do! We'll bury it!…"
Animals have parasites and diseases, so do plants, there are even bacteria that cann dissolve oil spills or plastic or what have you - why couldn't there be a disease living off magic - a magic item could be infected, losing power and speading the plague to other equipment it contacts, while a magic user would slowly lose his powers and contaminate all he works with or casts a spell at...