Quillbreaker Defense (Combat)Source Magical Marketplace pg. 6 (Amazon)
You know how to put armor spikes to defensive use by thrusting them into the path of an oncoming attack just in time.
Prerequisites: Proficiency with armor spikes.
Benefit: If you are wearing armor spikes, as an immediate action when you take damage from a nonmagical attack, you can give your armor spikes the broken condition to reduce the amount of damage you take by 5. If your armor spikes are already broken, they are destroyed when you take the damage. If you are wearing masterwork armor spikes, you instead reduce the damage taken by 10.Source Armor Master's Handbook pg. 21 (Amazon)
If you choose to spend 5 stamina points when using this feat, there is a 50% chance that your armor spikes do not gain the broken condition. This combat trick has no effect if your armor spikes already have the broken condition. (Magical Marketplace 6)