Vexing Vampire

Vexing Vampire gets +1/+1 for each creature
card in your graveyard.
At the beginning of your upkeep, you lose life
equal to Vexing Vampire's power.
Whenever an opponent casts a spell, you may exchange control of Vexing Vampire and that
spell. If you do, you may choose new targets for
the spell. (If the spell becomes a permanent, you
control that permanent.)