[Hubert waits patiently, his own impassive face and polite, faint smile never wavering. The child still wears her heart on her sleeve, but at least it's far subtler this time.]

I'm not entirely certain, I must admit. I've never witnessed it for myself.

[He idly toys with the pouch of iron, more for effect than any real fidgeting.]

It varies, from account to account, and possibly from Fae to Fae, but underlying commonality is that they seemed to be burned by it, and in some cases weakened. I'm unsure if that means a weakening of their body, or of their magic.

[He tucks the pouch away into a disguised pocket in his coat, and chuckles lowly.]

This is all hypothetical, of course.