Damage reduction

While Obsidian has not confirmed the existence of damage reduction in NWN2, it is a class feature of both the barbarian and warlock class which have been confirmed.

3.5 Damage reduction
Damage reduction is the ability of a creature to effectively "shrug off" or instantly regenerate damage done to it. Damage reduction can reduce damage to 0 but not below 0.

Defeating damage reduction
This ability is not a perfect protection as it is possible to still cause enough damage to overwhelm the ability, or bypasses it if certain conditions are met. The creature takes normal damage from energy attacks (even nonmagical ones), spells, spell-like abilities, and supernatural abilities.

Notation
Damage reduction is written as "value/type" where the "value" is a numeric number stating up to how much damage can be ignored each time the creature is injured and "type" is the condition which can bypass the ability.

e.g.

A creature with damage reduction 10/silver:
 * is struck with a weapon for 5 points of damage.
 * if the weapon is not made of silver, all the damage is completely ignored.
 * If the weapon is made of silver, the creature receives the full 5 points of damage.
 * is struck with a weapon for 17 points of damage.
 * if the weapon is not made of silver, the creature receives 7 (17-10) points of damage.
 * If the weapon is made of silver, the creature receives the full 17 points of damage.

Types
There are numerous different conditions which damage reduction can be bypassed with:
 * weapon material:
 * Cold iron. Creatures such as fey or demons.
 * Silver. Were-creatures or undead.
 * Adamantite. Golems and other metal creatures.
 * Alignment: Good, evil, lawful, chaotic etc. Usually this is not a specific alignment like chaotic-neutral.
 * Damage Type: piercing, bludgeoning, or slashing damage etc.
 * Enchantment:
 * Magic: Any weapon with at least a +1 magical enhancement bonus on attack and damage rolls. Such creatures’ natural weapons (but not their attacks with weapons) are treated as magic weapons for the purpose of overcoming damage reduction.
 * Epic: Magic weapons with at least a +6 enhancement bonus. Such creatures’ natural weapons are also treated as epic weapons for the purpose of overcoming damage reduction.
 * Multiple conditions:
 * OR conditions: A few creatures are harmed by more than one kind of weapon. A weapon of either type overcomes this damage reduction.
 * AND conditions: A weapon must be both types to overcome this damage reduction. A weapon that is only one type is still subject to damage reduction.

Some damage reduction has no bypass conditions. This is written has uses - (e.g. 5/-) and is always in effect.

Ammunition fired from a projectile weapon with an enhancement bonus is treated as a magic or epic weapon for the purpose of overcoming damage reduction. Similarly, ammunition fired from a projectile weapon with an alignment gains the alignment of that projectile weapon (in addition to any alignment it may already have).

Stacking
If a creature has damage reduction from more than one source, the two forms of damage reduction do not stack. Instead, the creature gets the benefit of the best damage reduction in a given situation.

e.g.

A creature with damage reduction 10/silver and 5/evil:
 * is struck with a weapon for 15 points of damage.
 * if the weapon is not made of silver nor evil-aligned, the creature receives 5 (15-10) points of damage.
 * If the weapon is only evil-aligned, the creature still receives only 5 points of damage.
 * If the weapon is only made of silver, the creature receives 10 (15-5)points of damage.
 * if the weapon is made of silver and evil-aligned, the creature receives the full 15 points of damage.

Preventing additional attack effects
Whenever damage reduction completely negates the damage from an attack, it also negates most special effects that accompany the attack, such as injury type poison, a monk’s stunning, and injury type disease. Damage reduction does not negate touch attacks, energy damage dealt along with an attack, or energy drains. Nor does it affect poisons or diseases delivered by inhalation, ingestion, or contact.

Attacks that deal no damage because of the target’s damage reduction do not disrupt spells.

Bypass sources

 * A monk's ki strike feature grants their unarmed attacks to meet some damage reduction conditions. At 4th level are treated as magic weapons, at 10th level they are treated as lawful and at 16th level they are treated as adamantine. Each upgrade does not replace the previous effect so at 16th level a monk's unarmed attack count as a magical, law-aligned adamantite weapon.
 * Spells may temporarily enhance attacks to meet the conditions of damage reduction, while weapons also provide more permanent methods.

NWN comparison

 * NWN's implementation of damage reduction only required a specific magic enchantment (e.g. +1 or +7 etc) to bypass damage reduction. This also included basic bonuses to-hit or damage not from enchantment (which provides both to-hit and damage bonuses).