Do you know of any mythical beings, that are hurt by odd items or materials? like buttons from a shirt or something, something that would not be usually considered a weapon, or a material you would usually not use for making weapons. I would like if you would provide an explanation, as to why do they have this weakness? If you don't know the reason, you can still mention it.
I want to focus on European mythology (any), but Mythology from other parts of the world are welcome.
I am looking for lethal or pain inducing weakness. I am not interested in weaknesses that deplete creatures stamina or help to contain it (like fenrirs' chains)
Vampires and werewolves are well known, please do not include them, unless they fit the parameters (which means no silver and no garlic vs. werewolves,vampires. We already know that.)