Mercia, Queen of Cherrystone

Vigilance, Groove 4 (Whenever this creature kills an opponent's creature in battle or another legendary
creature enters the battlefield, place 1 Groove Counter
on this creature (max 4).)
Remove 4 Groove Counters from Mercia, Queen
of Cherrystone: Gain 5 life and prevent the next 5 damage that would be dealt to creatures you
control this turn.