Mai, Jaded Edge

Prowess is a triggered ability. “Prowess” means “Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.”

If a creature has multiple instances of prowess, each triggers separately.

An exhaust ability is a special kind of activated ability. “Exhaust — [Cost]: [Effect]” means “[Cost]: [Effect]. Activate only once.”

An effect may allow you to take an action as long as you haven’t activated an exhaust ability this turn. Such an effect allows that action only if you haven’t begun to activate an exhaust ability this turn.