Mossborn Hydra + Agatha's Soul Cauldron + Fertilid + Crystalline Crawler

Mossborn Hydra

Agatha's Soul Cauldron

Fertilid

Crystalline Crawler

How it works

1. Activate Mossborn Hydra using Fertilid's ability 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, Mossborn Hydra triggers, doubling the number of +1/+1 counters on it.
3. Activate Mossborn Hydra twice using Crystalline Crawler's first ability by removing two +1/+1 counters from it, adding 1.
4. Repeat until there are no basic lands in your library.

This ingenious synergy transforms simple land-fetching into an exponential explosion of growth, all powered by Agatha's Soul Cauldron granting the activated abilities of our creature card graveyard to the rest of our board. Fertilid provides the engine to tutor basic lands straight to the battlefield, which in turn triggers Mossborn Hydra's landfall ability to double its counter count. Meanwhile, Crystalline Crawler acts as both the fuel source—sacrificing its own +1/+1 counters for mana to pay for Fertilid's activation—and the ultimate recipient to amass an overwhelming number of counters and near-infinite colored mana.