Hey guys, I've been brain storming a feat that uses exhaustion as a resource to get some extra oomph out of a fighter. This is my latest version. Do you feel this is balanced?
"Mastery over one's body allows them access to the deepest recesses of their bodily energy. You gain the ability to perform great feats which were otherwise impossible for you to perform at risk of exhaustion.
After choosing one of these benefits, you must make a DC 10 Constitution saving throw. On a failure, you gain one level of exhaustion. On a success, you do not gain exhaustion, but the DC of subsequent constitution saving throws for this feature increases by 5. The DC resets to 10 after you lose a level of exhaustion through a long rest or other means.
In addition to this, you gain proficiency in Athletics. If you are already proficient, you gain expertise."