Bone Heap

{t} add x {b} to your mana pool, where x is your devotion to black
{b}{t} exile target creature you control, put a death counter on this card
{b}{b}{b};this card becomes a 1/1 skeleton creature with indestructible until end of turn, with x +1/+1 counters, where x is the number of death counters on this card.
"Apparently, giving a graveyard sentience isn't a good idea."-Thuviel the Necromancer