“ 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...”
“ Swordbiters are parasites. They are long, thin and silver, and digest metal, somewhat like rust monsters, but smaller and more insidious. They resemble stick insects, but when they cling to metal they are very well camouflaged, and one can be biting your sword for a week before you notice it. They cannot be removed by hand, as they are very strong, but if the blade is inserted into fire they will leap off to escape the flames. Sometimes, old treasure hoards are infested with them, and the first glimpse you get of the 'glittering' weapons is a pile of rusted swords encrusted with these thin silvery insects.”
“ Want to avoid fighter types focusing on swords? Make Longswords and Bastardswords the weapon of the Noble class, with a death penalty for other to carry. These weapons will be ornate and finally crafted. Adventurers will be stuck with cheaply made broad and shortswords, while professional fighters might use two handed swords.”