When Petrified Field enters the battlefield, Kodama of the East Tree and Thranduil, Sindarin Liege trigger.
Resolve the Kodama of the East Tree trigger, putting nothing onto the battlefield.
Holding priority, activate Petrified Field's second ability by tapping and sacrificing it, returning Echoing Deeps from your graveyard to your hand.
Resolve the Thranduil, Sindarin Liege trigger, creating a token.
When the token enters the battlefield, Kodama of the East Tree triggers, putting Echoing Deeps from your hand onto the battlefield untapped as a copy of Petrified Field.
When Echoing Deeps enters the battlefield, Thranduil, Sindarin Liege triggers.
Holding priority, activate Echoing Deeps using Petrified Field's second ability by tapping and sacrificing it, returning Petrified Field from your graveyard to your hand.
Resolve the Thranduil, Sindarin Liege trigger, creating a token.
When the token enters the battlefield, Kodama of the East Tree triggers, putting Petrified Field from your hand onto the battlefield.
When Petrified Field enters the battlefield, Thranduil, Sindarin Liege triggers.
Repeat from step 4.
This elegant loop turns a simple land drop into an endless cascade of creature tokens by letting two lands trade places in the graveyard. Whenever a land enters the battlefield, Thranduil, Sindarin Liege provides the necessary Elf token to trigger Kodama of the East Tree, whose trigger allows you to cheat a land card directly from your hand. To keep the chain going, Petrified Field and Echoing Deeps seamlessly recur one another—with Echoing Deeps copying Petrified Field from the graveyard—while The Wandering Minstrel ensures every incoming land enters untapped to keep your mana open and your board state growing.