Improves your warforged fortification, granting you immunity to sneak attacks and extra damage from critical hits. However, you lose the ability to be healed by spells from the positive energy sub-school, such as Cure Light Wounds.
This Feat increases a Warforged characters natural Fortification by another 75%, but limits them to only being healed by Repair. This limitation should be considered in light of the Fortification bonus being available via item enchantment as well as the Warforged race already receiving a 25% bonus by the Light Fortification racial feat. Unless an arcane Repairer is in the party, you carry your own Repair potions, or you are able to Repair yourself otherwise, then this particular Feat will render your Warforged build unhealable except by Rest Shrine or the Repair Skill to revive you when you become incapacitated. (Compare with the Pale Master's Undead form and the Druid Dire Bear's spell, Unstoppable.)
Advice: Play in a group where this Feat will not work against the party's strategy.
- - forum discussion (2011)