Knight Gravecaller

As an additional cost to cast Knight Gravecaller,
you may discard a creature card.
Knight Gravecaller enters the battlefield with a
number of +1/+1 counters on it equal to the
mana value of the discarded card.
Whenever Knight Gravecaller attacks, you may
return a creature from your graveyard to play.
It gains decayed. You lose life equal to its mana
value.