Fortification

Fortification represents a percentage chance to negate a critical hit or sneak attack. When a critical hit is negated, damage is applied normally rather than at the critical hit multiplier. Fortification items stack with racial fortification of Warforged. Two standard fortification items which provide enhancement bonuses to fortification do not stack. Likewise two Exceptional Fortification items do stack either despite their confusingly named enchantment - as they provide Insight bonuses to fortification, and insight bonuses do not stack. Though one regular Fortification and one exceptional fortification item will stack with each other.

Since Update 13, monsters with sneak attack dice are able to bypass some of the player fortification equal to monsters' Challenge Rating. E.g.:
 * If a CR 1 Kobold Sneak attacks someone with 50% fortification, the Kobold Sneak has a 51% chance to normally conduct a critical hit or sneak attack.
 * If a CR 20 Lava Mephit attacks someone with 100% fortification, the Lava Mephit has a 20% chance to normally conduct a critical hit or sneak attack.
 * If a CR 54 Sellsword Footpad attacks someone with 150% fortification, the Sellsword Footpad has a 4% chance to normally conduct a critical hit or sneak attack.
 * If a CR 29 Earth Elemental attacks someone with 125% fortification, it is still going to have a 0% chance to critically hit or sneak attack, as it has no sneak attack dice.

Exceptional Fortification (10%)
Effect: Grants a +10% insight bonus to fortification, which protects against critical hits and sneak attacks. Note this bonus type does not match the name of the enchantment any longer.
 * Found on:
 * Toven's Hammer
 * Stalwart Trinket
 * Greater Stalwart Trinket
 * The Disciplinator
 * Sustaining Symbiont

Exceptional Fortification (25%)
Effect: Grants a +25% insight bonus to fortification, which protects against critical hits and sneak attacks. Note this bonus type does not match the name of the enchantment any longer.
 * Found on:
 * Omniscience

Exceptional Fortification (50%)
Effect: Grants a +50% insight bonus to fortification, which protects against critical hits and sneak attacks. Note this bonus type does not match the name of the enchantment any longer.
 * Found on:
 * Livewood Core (Level 24)
 * Leaves of the Forest (Level 24)

Construct Fortification (10%)
Effect: Grants a +10% insight bonus to fortification which protects against critical hits and sneak attacks. This enchantment is essentially identical to Exceptional Fortification (10%) despite the developers claiming it would be a useful stacking bonus, it is not.
 * Found on:
 * Docent of the Claw
 * Dragontouched Docent
 * Quorforged Docent of Battle
 * Docent of the Flames
 * Quorforged Docent of Battle (unsuppressed)

Stacking Fortification (25%)
Effect: Grants a +25% untyped bonus to fortification, which protects against critical hits and sneak attacks. Untyped bonuses stack.
 * Found on:
 * Fabricator's Bracers and Fabricator's Gauntlets worn as set, once Nearly Finished is unlocked.

Brace for Impact (+20%/+40%)
Effect: Passive Bonus: [+20/40]% untyped bonus to fortification. +[1/2] reflex/fort/will saves. Tier 1 Epic Destiny ability that can be purchased twice for a total of 40% fortification. Untyped bonuses stack.
 * Found on
 * Unyielding Sentinel