Editing Open4E:Defenses (section)

=Defenses=

Whenever a hostile action targets you, the attacker must make a check to see if the action affects you. The DC for this action is called a defense, and is based on one of your skills or abilities.

==Armor==
Your Armor defense is equal to your Reflex defense + your armor’s defensive value if you are wearing light armor, or your Fortitude defense + your armor’s defense value if you are wearing heavy armor. Most physical attacks, including basic melee and ranged attacks, target your Armor defense.

==Reflex==
Your Reflex defense is equal to 10 + your Dexterity modifier, and determines your ability to dodge out of the way of attacks. Many magical attacks target your Reflex. 

==Fortitude==
Your Fortitude defense is equal to 10 + your Constitution modifier, and determines your ability to withstand heavy blows, poisons, diseases, and magics that directly affect your life-force. While fewer attacks target your Fortitude than your Reflex, those that do can be much more dire.

==Will==
Your Will defense is equal to 10 + your Wisdom modifier, and determines your ability to withstand mental control, magical illusions, and psychic and morale attacks. Attacks that target Will tend to manipulate your behavior and perception, causing you to do things that you may not otherwise wish to do or forcing you to make choices that place you in great peril.

==Spot and Perception==
Finally, you have two additional “defenses” based on skills, which are used to determine whether you can see past attempts at stealth, illusion or deceit. Your Spot defense is equal to 10 + your Perception skill check modifier, and your Sense defense is equal to 10 + your Insight skill check modifier. Many skill effects, such as Stealth and Bluff, target your Spot or Sense defense, and these defenses determine how likely you are to notice particular features of any area that you are in.