Evasion

{{feat You can avoid even magical and unusual attacks with great agility. If you make a successful Reflex saving throw against an effect that normally deals half damage on a successful save, you instead take no damage.
 * icon=Feat_evasion_ranger.png‎
 * prerequisite= Monk 2 or Ranger 9 or Rogue 2
 * description=

Evasion can be used only if the character is wearing light armor or no armor, and is not heavily encumbered. A helpless character does not gain the benefit of evasion.

Evasion primarily helps against certain magic attacks as well as avoiding most types of trap damage. (The spell wards in Underdark adventures must be met by your Will save and cannot be evaded.) For avoiding most physical and ranged attacks, Dodge bonus chances are used.