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 as a copy of Petrified Field.
When Echoing Deeps enters the battlefield, Thranduil, Sindarin Liege and Tiller Engine trigger.
Resolve the Tiller Engine trigger, untapping Echoing Deeps.
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 creates an endless cycle of land sacrifices and resurrections by turning a single land drop into a continuous chain of triggers. Whenever a permanent enters, Kodama of the East Tree cheats cards from your hand into play, while Thranduil, Sindarin Liege provides the necessary entry fodder by churning out 1/1 Elf tokens with every landfall. Tiller Engine ensures your newly copied lands instantly untap and remain ready for action, allowing Petrified Field and Echoing Deeps to endlessly recycle one another from the graveyard.