There are few objects in Eem with more sinister properties than the kidney stone of a wyrm. While kidney stones are a relatively ordinary, albeit discomforting, condition faced by nearly every creature, once passed they are a benign byproduct of a painful physiological ordeal. This is not so for knobby, cruel, and venomous wyrms.
A wyrm is generally so viperous that their physical parts contain a little understood essence that drains the magic from any being, object, or place. Their hides, bones, organs, eyes, teeth, claws, and sinew are actually laced with a kind of poison that diminish the soul and shrivels the wonders of magic as effectively as salt would shrivel a snail. And in the case of Faerie folk, wizards, enchanters, and magicians–a wyrm’s kidney stone is the most potent piece of a most unpleasant beast–and can be so strong that the gift of magic may never come back.
How one acquires a Wyrm’s kidney stone is best left to one’s imagination, but the process is both hazardous and unpretty.