Yarok, the Desecrated + Fertilid + Crystalline Crawler + Avenger of Zendikar + Maskwood Nexus

Yarok, the Desecrated

Fertilid

Crystalline Crawler

Avenger of Zendikar

Maskwood Nexus

How it works

1. Activate Fertilid by paying 1 and removing a +1/+1 counter from it, causing you to search your library for a basic land card and put it onto the battlefield tapped.
2. When the land enters the battlefield, Avenger of Zendikar's second ability triggers twice, putting two +1/+1 counters on each creature you control.
3. Activate Crystalline Crawler's first ability twice by removing two +1/+1 counters from it, adding 1.
4. Repeat.

This clever land-searching loop is anchored by Yarok, the Desecrated, whose static ability doubles every single landfall and entering-the-battlefield trigger that occurs. Maskwood Nexus plays a subtle yet vital role by turning your creatures into every creature type, though here its primary function is working in tandem with the engine's core loop, where Fertilid fetches basic lands to continuously fuel Avenger of Zendikar's landfall triggers. Those extra lands and triggers pump up Crystalline Crawler, allowing you to strip away its counters for the exact mana needed to keep activating Fertilid while generating a massive army of Plants in the process.