Damage Reduction

Damage Reduction (DR) is a measure of how much damage a character can absorb before losing hit points. The DR value is subtracted from each incoming hit, to a minimum of zero damage received. If you have a DR 10 and get hit for 9 points of damage, you take no damage at all. If you have a DR 10 and get hit for 15 points of damage, you only take 5 points of damage. It is reported in the combat log as final/net damage dealt followed by damage reduced. DR applies only to physical weapon damage, although there is a similar concept of Resist Energy that applies to energy/elemental damage from spells and weapons.

Player characters (but not monsters, apparently) can gain "Active DR" when they are holding down shift to block. Active DR is a hidden quantity, but Passive DR is easily visible on the character sheet. Multiple DR entries will be listed, and only the highest one which is not bypassed by a particular attack's properties (like Adamantine) applies. Any Passive DR (from the single, highest applicable source) stacks with Active DR when actively blocking.

Another benefit of Active Blocking (any method; with or without shield) is that players are immune to special attacks and weapon effects. This includes, but is not limited to, Scorpion/Spider Poison and Wraith Constitution Drain. Blocking even makes players immune to extra weapon damage and effects, such as Crippling, Flaming, Wounding, Maladroit, or Bane!

Passive DR Sources
Passive DR can be provided from many sources, including:
 * Warforged Adamantine Body, Improved DR Feats, or Warforged Improved DR enhancements (DR/Adamantine)
 * Barbarians get +1 DR/- at levels 2, 5, 8, 11, 14 and a +1 Enhancement available at levels 4 and 7
 * Adamantine Armor DR/- (1 from shields or light armor, 2 from medium armor, and 3 from heavy armor)
 * Ironskin Chant (DR5/-) song from Warchanter Bard.
 * The Stoneskin spell (DR 10/Adamantine), Angelskin spell (DR5/Evil)
 * magical items of Invulnerability (DR 5/Magic), or of Axeblock, Hammerblock, and Spearblock
 * certain named items, like the Bloodrage Symbiont (DR5/-) or Golden Greaves (DR3/-)

These passive DR sources do not stack with each other; only the highest DR not overcome by the attack type is taken into account. But, if one type of DR is bypassed, a lower value DR from a different source can apply.

Example 1 - A Warforged Fighter has Adamantine Body and DR6/Adamantine and also has the temporary Ironskin Chant song DR5/- from a Bard in the party. He is hit with an Adamantine attack/weapon, which bypasses his DR6/Adamantine. But, he receives DR5/- from the Ironskin Chant.

Example 2 - The same WF Fighter is buffed with Stoneskin spell. The higher DR10/Adamantine replaces his own DR6/Adamantine until it runs out.

Any Passive DR (from the single highest, applicable source) stacks with Active DR when actively blocking. Passive DR that is bypassed is removed from the calculation.

Active DR Formula
Active Blocking DR = Passive DR + (with shield): [(BAB / 2) + 2 + Shield DR rating + Shield Enhancement Bonus + Shield Mastery Feats + Shield Mastery Enhancements] versus Ranged / 2 (w/ 2Weapons): [(BAB / 3) + 2 + Two-weapon Blocking Feat] versus Ranged / 4 (with other*): [(BAB / 5) + 1 + (no applicable feats)] *other is THF, Single weapon & no shield, or Unarmed and gives full DR versus Ranged attacks.

Active DR bonuses
The following Shield Mastery feats and enhancements are added onto the above base active DR value. They all stack.
 * Shield mastery +3
 * Improved shield mastery +3
 * Dwarven shield mastery +1, 2, or 3 (for levels I, II, and III of the enhancement)
 * Two-weapon blocking

Example 1 - A level 8 fighter with the regular and Improved shield mastery feats, actively blocking with a              +4 Heavy Adamantine Shield would have the following DR when using or blocking with shield: Passive DR vs. melee and ranged = DR1/- Active Blocking DR vs. melee = 1 + ([8/2) + 2 + 2 + 4 + 6] = DR19/- Active Blocking DR vs. ranged = 1 + [(8/2) + 2 + 2 + 4 + 6]/2 = DR10/-

Example 2 - The same level 8 fighter with two weapons would have the following DR: Passive DR vs. melee and ranged = none Active Blocking DR vs. melee = [(8/3) + 2] = DR4/- Active Blocking DR vs. ranged = [(8/3) + 2]/4 = DR1/-

Example 3 - A level 14 barbarian with innate DR5/-, a two-handed weapon (THF), and Stoneskin (DR10/Adamantine) would have the following DR: Passive DR vs. melee and ranged = DR10/Adamantine OR DR5/- For normal attacks he effectively has DR10. For Adamantine attacks he has DR5/-. Active Blocking DR vs. melee and ranged = [10 or 5] + [(14/5) + 1] = DR10/Adamantine OR DR5/- AND DR3/- For normal attacks he effectively has DR13. For Adamantine attacks he has DR8/-.

DR Aspects
While Active DR applies universally to all weapon physical damage and prevents special attack/effect damage, Passive DR may be bypassed by the properties of a particular attack. Some forms of DR are vulnerable to materials (like Adamantine or Silver), alignments (like Chaos or Good), or just "magic". In this case, the property which bypasses that DR is listed after the number on the character sheet, in the form of "DR 6/Adamantine" or "DR 5/Evil". If there is no property which can bypass the DR, a "-" is listed instead.

Monster DR
DDO includes monsters with Damage Reduction. Monster DR may require specific material, damage types, and/or alignment to bypass the DR and deal full damage. Additionally, some monsters are vulnerable to magic weapons only. Any weapon with at least a +1 magical enhancement bonus on attack and damage rolls overcomes the damage reduction of these monsters. For bypassing DR in DDO, material types are adamantine, byeshk, cold iron, flametouched iron, and silver. Damage types are bludgeoning, piercing, slashing. And alignment are Law, Chaos, Good, Evil. A Transmuting weapon is enchanted to mimic all material/damage/alignment types and can bypass any DR that can be bypassed (but not DR/-).

Some examples include:
 * Clay Golems require Bludgeoning and Adamantine weapons
 * Flesh Renders require Good Aligned and Cold Iron weapons
 * Ghostly Skeletons require Good Aligned weapons
 * Iron Golems and Flesh Golems require Adamantine weapons
 * Rakshasas require Good Aligned and Piercing weapons
 * Skeletons require Bludgeoning weapons
 * Vampires require Silver weapons
 * Zombies require Slashing weapons