Pinnacle of Mortality

Session after session of relentless training at the Flex Forge's gyms have pushed your body to the peak of its potential. Choose one focus: Strength, Dexterity, or Constitution, you then gain one of the following benefits, depending on the focus you chose:

[Strength] Conditioned Core: You count as one size larger for carrying capacity, and you add half your proficiency bonus (rounded down) to any Strength check or Save made to resist being moved, knocked prone, or grappled. 

[Dexterity] Acrobatic Mastery: You can traverse narrow ledges, climb, or balance without a reduction to speed. You can also move through the space of other creatures without any kind of penalty.

[Constitution] Enduring Spirit: You can go twice as long without food, water, or sleep before suffering exhaustion. When you finish a short rest, you recover one level of exhaustion.

Pushing Beyond Limits: Once per turn, when you are about to make an attack roll, saving throw, or ability check using Strength, Dexterity, or Constitution, you can choose to push yourself beyond safe limits, rolling a d6 and adding the result to your roll. This effort is incredibly straining for the body, making it so that some muscle fibers get teared apart on the process,you then take an amount of slashing damage equal to three times your proficiency bonus. This damage can't be reduced or avoided in any way.