When Gruul Turf enters the battlefield, it, The Necrobloom, and Kodama of the East Tree trigger.
Resolve the Kodama of the East Tree trigger, choosing not to put anything from your hand onto the battlefield.
Resolve the Gruul Turf trigger, returning it from the battlefield to your hand.
Resolve the The Necrobloom trigger, creating a token.
When the token enters the battlefield, Kodama triggers, putting Gruul Turf from your hand onto the battlefield.
When Gruul Turf enters the battlefield, it and The Necrobloom trigger.
Repeat from step 4.
This ingenious loop turns a simple bounce land into a self-sustaining engine by utilizing Kodama of the East Tree as a bridge between tokens and permanents. Every time Gruul Turf enters the battlefield to trigger its own return, it simultaneously sets off Kodama of the East Tree and The Necrobloom, allowing The Necrobloom to spawn a token that immediately satisfies Kodama of the East Tree's entry condition. By stacking these triggers correctly, the token's arrival lets you drop Gruul Turf right back onto the battlefield from your hand without spending any extra mana.