Cradle of Bones

Whenever a creature you control dies, put a bone counter on Cradle of Bones.
Remove a bone counter from Cradle of Bones:
Draw a card, then discard a card.
Remove X bone counters from Cradle of Bones:
Return target creature card with converted mana
cost X or less from your graveyard to the battlefield. Activate this ability only any time you
could cast a sorcery.