When Petrified Field enters the battlefield, Kodama of the East Tree and Dancing from Dark to Dawn 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 Dancing from Dark to Dawn 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, Dancing from Dark to Dawn 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 Dancing from Dark to Dawn 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, Dancing from Dark to Dawn triggers.
Repeat from step 4.
This ingenious loop relies on a clever recursive exchange between two lands, cycling Petrified Field and Echoing Deeps back and forth from the graveyard to the battlefield. As each land enters, Kodama of the East Tree spots the landfall trigger from Dancing from Dark to Dawn, using the resulting Bear token's arrival to sneak the other land directly out of your hand. Meanwhile, the static ability of Archelos, Lagoon Mystic ensures these lands enter the battlefield untapped, allowing you to sacrifice them immediately for mana or to activate their recursion abilities on the spot.