Boom Scholar
Exhaust abilities of other permanents you control cost 
less to activate.
Exhaust — 
: Creatures and Vehicles you control gain trample until end of turn. Put two +1/+1 counters on this creature. (Activate each exhaust ability only once.)
Illustrated by Brian Valeza
This printing
Prices
If an ability triggers whenever you activate an exhaust ability, that ability resolves before the exhaust ability resolves.
If an exhaust ability of a permanent is activated, and then that permanent leaves the battlefield and returns to the battlefield, it becomes a new object so its exhaust ability can be activated again.
Exhaust abilities can be activated any time you could normally activate an ability.
Boom Scholar’s first ability can cause the mana component of the cost to activate an ability to be
.
