Voidseer's Quest

Enchant creature.
At the beginning of each end step, if four or more cards were put into graveyards this turn, put a +1/+1 counter on enchanted creature.
Sacrifice enchanted creature: Cast target spell in a graveyard with converted mana cost less than enchanted creature's power without paying it's mana cost. Activate this ability only if there are 3 or more +1/+1 counters on enchanted creature.