Armor as Damage Reduction

Armor in this system keeps all of its normal statistics and qualities, but its armor bonus (including any enhancement bonus added to armor bonus and natural armor bonus ) is converted to DR/armor. The DR an armor provides is equal to its total armor bonus with a +1 bonus at 5th level or at 5 Hit Dice, with an increase to that bonus of +1 for every five levels above 5th level, or every 5 Hit Dice over 5 Hit Dice (to a maximum of +4 to DR at 20th level or at 20 or more Hit Dice ), provided that the creature wearing the armor is also proficient with the armor.

Using Armor without Proficiency: Creatures using armor they are not proficient with do not gain the bonus per level or Hit Dice to the DR, on top of any of the other normal penalties for using armor without proficiency.

DR/Armor: This type of DR blocks the damage of all attacks that would normally be affected by DR, based on the composition of the armor (see Table: Armor Composition and DR). Unlike most forms of damage reduction, DR/armor stacks with other types of DR. For instances, when fighting a skeleton with DR 5/bludgeoning and DR 4/armor (+2 for armor, +2 for natural armor ), the skeleton’s DR/armor reduces 9 points of damage from non-bludgeoning attacks, and 4 damage from bludgeoning weapon attacks. Magic weapons and attacks from Large or larger creatures bypass the DR 4/armor, but not the DR 5/bludgeoning.

Natural Armor Bonus and DR: Like a creature’s armor bonus, a natural armor bonus is also converted into damage reduction. If a creature is wearing armor and has a natural armor bonus, the creature adds its armor bonus to its natural armor bonus to determine the amount of DR/armor that it has (see
Table: Natural Armor Conversion to DR).

For instance, if a creature wearing a +2 chain shirt has DR 6/armor is then subject to a barkskin spell cast by a 6th-level druid (gaining a +3 natural armor bonus ), its DR becomes DR 9/armor for the duration of the spell. This DR is bypassed by adamantine, or the attacks of Huge or larger creatures. A creature that has both DR from a source other than armor and a natural armor bonus gains the effects of an enhanced form of DR, similar to how the composition of the armor grants special DR/armor defenses (see Table: Armor Composition and DR). If a creature has magical armor, natural armor, and DR, it takes the best form of the special protection provided by both its armor and its mix of DR and natural armor to its DR/armor. For instance, if a creature has natural armor and DR/magic and is wearing adamantine armor, that creature’s DR/armor functions as DR/—, and can be bypassed by Gargantuan or larger creatures, since the adamantine armor provides the best of the two damage reductions.

Unusual Creatures and Armor DR: Amorphous or incorporeal creatures have an easier time bypassing DR/armor. When they attack a creature with DR/armor, they typically treat that DR as a fraction of the DR/armor. Attacks by incorporeal creatures entirely ignore the DR unless that DR comes from a force effect or from armor with the ghost touch special armor quality. These traits are detailed in Table: Unusual Creatures and Armor DR.

Critical Hits and Defense

When a creature threatens a critical hit, it does not make a critical hit confirmation roll. Instead, the target of that critical hit makes a critical defense check instead. A critical defense check is 1d20 + a bonus equal to the creature’s DR + the creature’s Dexterity modifier (up to the maximum Dexterity bonus allowed by any armor worn) + the sum of any deflection and shield bonus to Defense.

Critical defense check bonus = creature’s DR + Dexterity modifier + shield bonus to Defense + deflection bonus

The DC of the check is based on the die roll for the critical threat. It is further modified by the base attack bonus of the attacking creature, how many Critical Feats the attacking creature has (if any; 10 maximum), and a bonus relationship between the size of the attacking creature and the target of the critical hit, if the attacking creature is larger than the creature it attacked.

Critical defense DC = critical hit roll + 1/2 attacker’s base attack bonus + 1 for each critical feat + 1 for each size category larger attacker is than target

For instance, if a Medium creature is hit with a crossbow fired by a Medium 6th-level fighter with two Critical Feats, and the critical threat attack roll is a 19, the target of the potential critical hit makes a critical defense check with a DC of 24 to reduce the critical hit to a normal hit. If the target is wearing +1 leather armor, has a Dexterity of 18, and is using a +1 buckler, that target would have a +9 bonus on the critical defense check to reduce the critical hit to a normal hit. On a roll of 15 or higher, the critical hit is reduced to a normal hit, and the target takes normal damage for the hit (which is reduced by its DR). If the creature firing the crossbow had rolled a 20, the target of the critical hit would need to roll a 16 or higher on its critical defense check to reduce the impact of the critical hit, making it a normal hit.

On a failed critical defense check, the target of the critical hit takes the damage for the critical hit. That damage is still reduced by the target of the critical hit’s DR.

Fortification Special Armor Quality: The fortification special armor quality acts in concert with the check, coming into play if the armor check fails.

Table: Armor Composition and DR

Material DR Provided Attacker Size to Bypass DR
Nonmagical armor1 DR/magic Large
Magical armor1 DR/adamantine Huge
Adamantine armor1 DR/— Gargantuan

1 Brilliant energy weapons bypass any DR provided by armor. In addition, DR from armor is halved if a creature is grappled or entangled, and does not apply when a creature is helpless or pinned.

Table: Natural Armor Conversion to DR

Natural Armor/DR DR Provided Attacker Size to Bypass DR
Natural armor DR/magic Large
Natural armor with DR/magic DR/adamantine Huge
Natural armor with DR/adamantine DR/- Gargantuan
Natural armor with DR/- DR/-1 Colossal
Natural armor with DR/epic DR/epic1 n/a

1 A creature that already has DR/— or DR/epic increases its DR by an amount equal to its natural armor bonus.

Table: Unusual Creatures and Armor DR

Attacking Creature Type DR Modifier
Amorphous1 -
Incorporeal ×0 (×1 if DR is from a force effect or ghost touch armor)
Swarm of Tiny creatures ×1/2
Swarm of Diminutive creatures ×1/4
Swarm of Fine creatures ×0

1 Elementals, oozes, oozelike creatures, and any creature with the amorphous defensive ability.

Armor as Damage Reduction

The First Root Tesoe