Xerath, the Magus Ascendant

Mage (This creature enters the battlefield with an AP
counter on it. {2}, {t}: This creature deals damage
equal to the number of AP counters on it to target
creature you don't control. Activate this ability only
during a combat phase.)
Whenever Xerath activates an ability, you may
pay {u/b}{u/b}. If you do, copy that ability. You may
choose new targets for the copy.
"I will be free."