ENDURANCE
Types: Combat, General, Tier 1.
Prerequisites: Constitution.
Benefits: You can go twice as long holding your breath, forced marching, running, swimming, going without food and water, enduring hot or cold environments, etc. before you need to start making any Constitution or Swim checks or Fortitude saves to resist nonlethal damage, fatigue, exhaustion, etc. You may sleep in light or medium armor without becoming fatigued. You treat the duration as half as long for the purposes of calculating DCs for these checks and saves as well.

IMPROVED ENDURANCE
Types: Combat, General, Tier 2.
Prerequisites: Constitution, Endurance.
Benefits: You are permanently affected as if by the Endure Elements spell using your character level as caster level. This is a supernatural effect.

GREATER ENDURANCE
Types: Combat, General, Tier 3.
Prerequisites: Constitution, Endurance, Improved Endurance.
Benefits: You gain damage resistance equal to 1/4 your level against any damage caused by any effect the Endurance feat applies to.