Fertilid + Felidar Retreat + Tireless Provisioner + Horizon Explorer

Fertilid

Felidar Retreat

Tireless Provisioner

Horizon Explorer

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 on the battlefield untapped due to Horizon Explorer.
2. When the basic land enters, Tireless Provisioner and Felidar Retreat trigger.
3. Resolve the Tireless Provisioner trigger, creating a Treasure token.
4. Activate the Treasure by tapping and sacrificing it, adding .
5. Resolve the Felidar Retreat trigger, putting a +1/+1 counter on Fertilid.
6. Activate the basic land by tapping it, adding 1.
7. Repeat.

This elegant loop turns a modest land-searcher into a full library harvest by recycling its own fuel. With Horizon Explorer ensuring your lands enter untapped, every search puts a land directly onto the battlefield to power your engine. That new arrival triggers Tireless Provisioner to generate a Treasure token for mana, while Felidar Retreat simultaneously replaces the +1/+1 counter that Fertilid spent to start the process. The mana from the Treasure and the land covers Fertilid's activation cost, letting you continuously repeat the cycle until every basic land from your deck is on the battlefield.