{C} Nemesis of Mortals [Theros][THS 163]

This spell costs {1} less to cast for each creature card in your graveyard.
{7}: Monstrosity 5. This ability costs {1} less to activate for each creature card in your graveyard. (If this creature isn't monstrous, put five +1/+1 counters on it and it becomes monstrous.)