Undercity Cultist

Undergrowth - When Undercity Cultist enters the battlefield or transforms, create X 1/1 black human rouges with deathtouch where X is the number of creature cards in your graveyard.
{x}{b/g}, Sacrifice A Creature: Search anywhere for a green or a black card with a converted mana cost of X or less and put in play under your control.
On each upkeep, if no spells were cast last turn, transform Undercity Cultist.