You have at least six other cards in your graveyard.
Mana Needed
({4} magic symbol) ({B} magic symbol) ({G} magic symbol) each other turn available.
Steps
Cast
Polukranos Unchained from your graveyard for its escape cost by paying ({4} magic symbol) ({B} magic symbol) ({G} magic symbol) and exiling six other cards from your graveyard, causing it to enter the battlefield with twelve +1/+1 counters on it.