I've spent quite a bit of time on Google today:
Q: Can falling down the stairs kill you?
A: It depends on how you land, how many stairs, etc.
Q: Are bruises from life still going to be there after the person has died granted they hadn't healed yet?
A: Um, I think so? That was one where I didn't get a lot of good answers. I guess if a person had gotten beaten to death, the bruises and cuts (or whatever) would still be visible.
Q: What were the hilts of swords made from?
A: The grip was made out of, according to Wikipedia, wood or metal, but with something covering it, like sharkskin. Interesting.
Q: How long ago was it discovered that people have iron in their blood?
A: still working on it.
I'm not so original as to my faeries having a weakness other than iron. Quite frankly, iron works for me as a good weakness. Except perhaps, the iron doesn't have to be pure. Steel works good. Ditto with silver for werewolves and other creatures of the night.
Ironically, silver and iron don't make an alloy. Drat. It'd be like the Super Weapon.
I bet my MC could figure something out... I guess that's a plus to writing fantasy. I could make up a Super Metal.
But that's neither here nor there.