Damage reduction

Description
Absorption is an effect found on some Warrior-specific equipment that reduces damage. Some, but not all sources of absorption are global; they will reduce damage no matter which part of the body is hit. There are three main sources of absorption: armor, runes, and shields.

Armor
Ascalon Armor and Knight's Armor reduce physical damage taken by 3. This effect is not global, and the damage reduction only applies to hits taken on area of the body covered by knights or ascalon armor.

Runes
Runes of Absorption reduce damage by 1-3 depending on potency. Minor Runes of Absorption reduce 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. Like all runes, Runes of Absorption do not stack with each other, even though they do not have (non-stacking) in their description like the absorption armors or other types of runes.

Shields
Shields may have up to two reduction modifiers, each with different requirements. Damage from all sources are reduced, even those that armor absorption doesn't reduce. 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.

Quests and Collectors
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.

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).