You’ve reached a milestone in your cardiovascular potential, allowing you to push past the point of exhaustion without stopping.

Whenever you roll a saving throw to avoid taking a level of Exhaustion, roll your Mastery Dice and add the rolled amount to the saving throw. If the effect does not specify or allow a saving throw (such as the Path of the Berserker’s Frenzy), you instead make a Constitution saving throw against your Mastery DC (you may add your Mastery dice roll to this save as well). If you succeed, you do not take a level of Exhaustion.