This brilliant loop grants you infinite turns by recycling a single extra-turn spell through recurring creature tokens. When you cast Walk the Aeons, you secure the extra turn you need to set up your board state. Then, you declare attackers with Phantom Steed, whose trigger brings in a temporary, attacking token copy of Greenwarden of Murasa. The entering token's ability immediately plucks Walk the Aeons right back out of your graveyard and into your hand, ready to be cast again on your next turn.