Defense (PSR Supplement)

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Your defense (or “AC”) is a number that represents how difficult you are to hit with attacks. When a creature makes an attack targeting you, that creature makes an attack roll. The attack hits if the roll's result equals or exceeds your defense.

Normally your defense equals 8 + your PB + your Dexterity modifier + your total armor bonus, to a maximum of 25.

Armor. Armor includes any attire you're wearing that increases your defense. These increases are called armor bonuses, and all of them summed together is your total armor bonus. Sometimes other effects can grant an armor bonus which adds to this total.

Shield. A shield bonus can increase your defense further, potentially over 25. Normally this is gained by wielding a shield, but similar effects that deflect incoming attacks can also grant a shield bonus. Shield bonuses don't combine; only the highest bonus applies.

Cover. Cover can also increase your defense over 25. Cover doesn't combine; only the greatest cover applies.

Other Modifiers. Within PSR, very few effects increase your defense outside of armor, shield, and cover. A few can decrease from it. There are some circumstances that fundamentally change your defense, including the following:

• Wearing heavy armor limits how much of your Dexterity modifier is added to your defense.
• Some effects let you add a different ability modifier to your defense instead of Dexterity. The limit from heavy armor still applies to this ability modifier.
• You might have an effect like, "You have a natural armor of +4. You add either this natural armor bonus or your total armor bonus to your defense, whichever is higher."
• You might have an effect like, "Your defense becomes 17 if it would otherwise be lower." Due to how this works, no modifiers apply; not a shield bonus, not cover, but also not any negative modifiers.

Everything Has Defense. All creatures and objects each have their own defense. Any NPC's defense is included in its stat block. For objects, defense instead represents how difficult it is to damage, rather than how difficult it is to hit. Wood has greater defense than paper, and steel has greater defense than wood, for example. See Damaging Objects.