What it does
Exhaust is an ability word that marks abilities you can only activate once per game. Each "Exhaust —" ability on a permanent has its own once-per-game limit, so a card with two different exhaust abilities lets you use each one a single time. They're typically powerful payoffs balanced by that hard cap.
The most common mistake is thinking the limit resets somehow—it doesn't. Once you've used an exhaust ability, that specific ability is spent for the rest of the game, even if the permanent leaves and returns to the battlefield. A new copy or a re-cast version of the same card, however, is a separate object and gets its own use.
In Commander, exhaust abilities reward building around blink or recursion: returning the permanent gives you a fresh object and another activation. They also pair well with copying effects, since each token copy carries its own untapped exhaust ability.













