You have at least six other cards in your graveyard.
({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.
Activate Altar of Dementia by sacrificing Polukranos Unchained.
When Polukranos Unchained dies, The Ozolith's first ability triggers, putting twelve +1/+1 counters on it.
Resolve the Altar of Dementia ability, causing you to mill cards equal to Polukranos Unchained's power.
At the beginning of your combat phase, The Ozolith's second ability triggers, moving the +1/+1 counters from it onto Sage of Hours.
Activate Sage of Hours by removing all +1/+1 counters from it, causing you to take at least two extra turns after this one.