Steadfast Determination
( Player's Handbook II, p. 83)[General]
Your physical durability allows you to shrug off attacks that would cripple a lesser person. Rather than depend on agility or willpower, you use your raw toughness to survive.
Prerequisite
Endurance (PH) ,
Benefit
You can use your Constitution modifier in place of your Wisdom modifier on Will saves. You do not automatically fail Fortitude saves on a roll of natural 1.