Endurance

Gain +4 bonus on following checks & saves: Swim checks made to resist nonlethal damage from exhaustion; CON checks to continue running;
CON checks to avoid nonlethal damage from a
forced march; CON checks to hold your breath;
CON checks to avoid nonlethal damage from starvation or thirst; Fort saves to avoid nonlethal damage from hot or cold environments;
& Fort saves to resist damage from suffocation.
You may sleep in light or medium armor without becoming fatigued.