Rel'la

Champion a creature (When this creature enters the
battlefield, sacrifice it unless you exile another creature
you control. When this creature leaves the battlefield,
that card returns to the battlefield.)
Whenever a spell or ability you control causes a
creature an opponent controls to go the graveyard,
Rel'la deals 1 damage to that creature's controller.
Sacrifice a creature: Rel'la deals 1 damage to
target creature.