"Whats this do?" Asked the visting Human.
"That," Dugfar replied. "Is my- Wait! Don’t tou-"
...and with that they were buried alive.
The proud dwarven Captain Dugfar stood atop his mighty machine of magic and stone looking down the mountain they had just emerged from; letting the wind whip his beard over his shoulder… "This is a proud day for the Dwarves!" He bellowed. "...and this is just the start!"
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...