Poltrus, Keeper of Dark Magic

Flying, Hexproof
Whenever you pay life, put a blood counter on
this creature.
{t}, Pay 2 life: Return target instant or sorcery
from your graveyard to the top of your library.
{t}, Pay 4 life: Destroy target creature with power
less than the number of Blood counters
on Poltrus, Keeper of Dark Magic.