D20 Mechanic: Defenses

This section outlines the concept of defenses, a combination of d20 armor class and saving throws, and some mechanics from D&D 4e. Most of the concepts herein are taken from those two systems.

Overview

Creatures have four sets of defenses: fortitude, reflex, will, and determination.

Each of these two values have two components: the defense and saving throw.

Defenses

Generally, when you are subject to an unusual or magical attack, you get a saving throw to avoid or reduce the effect. Like an attack roll, a saving throw is a d20 roll plus a bonus based on your class, level, and an ability score. Your saving throw modifier is:

Base save bonus + armor bonus + ability modifier

Base Save Bonus: A saving throw modifier derived from character class and level. Base save bonuses increase at different rates for different character classes. Base save bonuses gained from different classes, such as when a character is a multiclass character, stack.

Armor Bonus: Each type of armor provides a bonus to some of your saving throws.

In addition to having a saving throw, you also have a defense value for each of these categories. That is calculated as follows:

10 + base save bonus + armor bonus + ability modifier

Some effects will call for a saving throw, while others will be against your defense of a given type. You cannot choose which of these values to use; a given effect will indicate whether it allows for a saving throw, or is against a given defense.

Defense vs. Saving Throw

To clarify the purpose of defenses and saving throws, this section will provide general advice as to when defenses and saving throws are used.

Defenses: When an effect is being produced, it will usually be against your defense. If a mage casts firaja at you, the mage will make a magical attack roll against your Reflex defense.

Saving Throws: Saving throws are typically used to overcome status effects. If a mage casts firaja at you and you gain ongoing fire damage as a result, you can make Reflex saving throws during your turn to end the ongoing fire damage.

Types

Fortitude 

These saves measure your ability to stand up to physical punishment or attacks against your vitality and health. Apply the better of your Strength modifier or your Constitution modifier to your Fortitude saving throws.

Reflex 

These saves test your ability to dodge area attacks. Apply the better of your Dexterity modifier or your Perception modifier to your Reflex saving throws.

Will 

These saves reflect your resistance to mental influence as well as many magical effects. Apply the better of your Intelligence modifier or your Wisdom modifier or your to your Will saving throws.

Determination 

These saves reflect your ability to follow your goals and take action in the face of danger. Apply the better of your Bravery modifier or your Charisma modifier to your Determination saving throws.

Defense Effects

There are a number of abilities that impact how your defenses function, which are outlined here.

Evasion

Evasion represents an uncanny ability to quickly remove yourself from danger. It impacts your Reflex.

Evasion

If you make a successful Reflex saving throw against an attack that normally deals half damage on a successful save, you instead takes no damage; if the effect has a partial effect on a successful saving throw, you instead suffer no effect.

Evasion can be used only if you are not helpless or prone.

You gain a +2 bonus to your Reflex Defense.

Improved Evasion

As per Evasion, but in addition, when you fail a Reflex saving throw against an attack or effect, you are instead treated as though having succeeded (though without the benefits of Evasion).

Your bonus to your Reflex Defense increases to +5.

Perfect Evasion

You ignore all detrimental effects that call for a Reflex save.

Your bonus to your Reflex Defense increases to +10.

Grit

Grit represents a profound ability to withstand physical trauma. It impacts your Fortitude.

Grit

If you make a successful Fortitude saving throw against an attack that normally deals half damage on a successful save, you instead takes no damage; if the effect has a partial effect on a successful saving throw, you instead suffer no effect.

Grit can be used only if you are not unconscious.

You gain a +2 bonus to your Fortitude Defense.

Improved Grit

As per Grit, but in addition, when you fail a Fortitude saving throw against an attack or effect, you are instead treated as though having succeeded (though without the benefits of Grit).

Your bonus to your Fortitude Defense increases to +5.

Perfect Grit

You ignore all detrimental effects that call for a Fortitude save.

Your bonus to your Fortitude Defense increases to +10.

Mettle

Mettle represents your mental composure and ability to maintain yourself. It impacts your Will.

Mettle

If you make a successful Will saving throw against an attack that normally deals half damage on a successful save, you instead takes no damage; if the effect has a partial effect on a successful saving throw, you instead suffer no effect.

Mettle can be used only if you are not dazed, stunned, confused, or dominated.

You gain a +2 bonus to your Will Defense.

Improved Mettle

As per Mettle, but in addition, when you fail a Will saving throw against an attack or effect, you are instead treated as though having succeeded (though without the benefits of Mettle).

Your bonus to your Will Defense increases to +5.

Perfect Mettle

You ignore all detrimental effects that call for a Will save.

Your bonus to your Will Defense increases to +10.

Tenacity

Tenacity represents your inner drive to succeed in the face of all odds. It impacts your Determination.

Tenacity

If you make a successful Determination saving throw against an attack that normally deals half damage on a successful save, you instead takes no damage; if the effect has a partial effect on a successful saving throw, you instead suffer no effect.

Tenacity can be used only if you are not cowering, frightened, helpless, panicked, or shaken.

You gain a +2 bonus to your Determination Defense.

Improved Tenacity

As per Tenacity, but in addition, when you fail a Determination saving throw against an attack or effect, you are instead treated as though having succeeded (though without the benefits of Tenacity).

Your bonus to your Determination Defense increases to +5.

Perfect Tenacity

You ignore all detrimental effects that call for a Determination save.

Your bonus to your Determination Defense increases to +10.