I was going to do that, but wanted to expand it to a Power, something that could be used for multiple things not just Fae and Iron. This is the rough version i am using. Bear in mind, my setting Fae are quite different, took inspiration from half a dozen different sources and created a new version of them. Finially finished with the PDF of it, almost 70 pages. The power is something i am still working on, and will add when i have it perfected.
Frailties [+1]
Description: Frailties are limitations on one’s power, similar to a catch. Like a catch, Frailties run the gamut from something like Iron to silver to rose petals to holy ground. Frailties are in essence a limitation one one’s power, your powers may not work as well when touching such things, may be weakened by them, might not be able to work at all or your character could even be harmed by your frailty.
Must: Must select one or more powers that are affected by your frailty when you purchase this power. Any power from the following groups may be affected, Faerie Magic, Minor Talents, Psychic Abilities, Shapeshifting, Spellcraft and Vampirism.
Skills Affected: Varies
Effects:
Weakened by Touch: When you are touching your Frailty, all your powers affected by it are harder to use and maintain, resulting in a -2 on all rolls to use or sustain your powers.
Immunity to Power [+1]: You cannot affect your Frailty in any way with your powers, any attempts too always fail. In addition when in the presence of high quantities of your Frailty or your target is carrying a large amount of your Frailty, your powers are weakened in the same way as if you were touching it.
Physically Weakened [+1]: Not only does your Frailty weaken your powers, but it also weakens you physically. For every scene you are touching your Frailty, one of your mental stress boxes fill, or if you have hunger stress, one of those boxes fill instead. If you possess any Toughness or Recovery Powers, you must take your Frailty as a Catch.