Greenwatcher

Your experience fighting against and alongside fey creatures is nearly unrivaled. Any weapon you wield or unarmed attack you make against a fey creature is treated as cold iron. Whenever you critically fail a save against a spell cast by a fey creature, it's instead treated as a normal failure. Whenever you critically succeed on a Strike against a fey creature, the target is immediately subject to the effects of a Faerie Fire spell. For the purposes of counteracting this effect, it's an innate 2nd-rank primal spell.