When you make a successful Reflex save to avoid damage, you suffer no damage instead of half damage.
Evasion primarily helps against certain magic attacks as well as avoiding most types of trap damage. (The Spell wards in The 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.
Sources of evasion
- Monk 2, Ranger 9, Rogue 2 - Class Special Feat
- Alchemist 12 that takes the feat Liquid Luck
- Druid Nature's Warrior tier 5 ability Swift Hunter (Requires Wolf Form)
- Shadow Mastery - Shadowdancer core ability
- Evasive Manoeuvres - Swashbuckler sixth core ability
- Natural Evasion - Primal Avatar tier four ability
- Past Life: Disciple of the Fist - Monk Active Past Life feat - a 20-second activated duration
The following situations prevent evasion:
- Wearing medium or heavy armor
- Carrying large or tower shield
- Being heavily encumbered
- Being helpless
There is no warning that you have lost evasion until you try to use it and cannot. Then, a text message appears at the top of the screen: "EVASION FAILED.
You cannot evade <reason>"