Damage reduction

Description
Absorption or damage reduction is an effect found on some shields, focus items and Warrior-specific equipment that reduces physical damage, provided from some Enchantments against all types of damage and provided by the Lightbringer title effect against all types of damage from certain foes. All sources of absorption except for Knight's/Ascalon Armor are global; they will reduce damage no matter which part of the body is hit. There are five main sources of absorption: Warrior Armor, Runes, Shields, Focus items and Enchantments.

It is also

Armor
Warrior Prophecies Ascalon Armor and Warrior Knight's Armor (Knight's armor function) reduce physical damage taken by 3, as does the Knight's Insignia. This effect is not global, and the damage reduction only applies to hits taken on area of the body covered by Knights or (Warrior) Ascalon armor. The absorption was global prior to the July 13th 2006 update.

Runes
Runes of Absorption reduce damage by 1-3 depending on potency. Minor Runes of Absorption reduce physical damage by 1, Major by 2, and Superior by 3. Runes of Absorption only reduce damage from physical damage and have no effect on spells or other sources of damage. Runes of Absorption do not stack with each other. This effect is global.

Shields
Shields may have up to two of the four different physical damage reduction modifiers, each with different requirements. Only physical damage is reduced since the July 13th 2006 update. Before this update all kinds of damage got reduced. Two absorption modifiers on the same shield will stack so long as both requirements are met. Shield absorption is global and does not depend on which direction you are hit from.

Focus items
Focus items obtained in the Nightfall Campaign or created through the PvP Equipment panel can have any one of the four physical damage reduction modifiers available on Shields.

Quest and Collector items
Some quests and collectors may provide items with absorption properties, such as Blankets for the Settlers, Ruins of Surmia, or Martel Bastions. These modifiers are similar to shield absorption modifiers and will reduce damage so long as their requirements are met. However, this kind of damage absorption is not a property found on dropped items, so do not expect to find a dropped weapon with an absorption effect.

Enchantments
Multiple Enchantments provide damage reduction, some of which are Shield of Absorption, Shielding Hands, Stoneflesh Aura and Armor of Sanctity.

Enchantments
Many Enchantments provide damage reduction, some of which are Shield of Absorption, Shielding Hands and Armor of Sanctity. Shield of Absorption and Shielding Hands reduce damage from all sources, while Armor of Sanctity only reduces damage from foes who are suffering from conditions.

Lightbringer title
The effects of the Lightbringer title reduce damage of all types, but only reduces damage from demonic servans of Abaddon.

Absorption chart
A list of the most common sources of absorption: Note that the 1-10% chance shields are from before the March 02, 2006 update which increased the maximum from -3 (10% chance) to -5 (20% chance).