Szarel, Genesis Shepherd + Crystalline Crawler + Slimefoot and Squee + Umbral Collar Zealot

Szarel, Genesis Shepherd

Crystalline Crawler

Slimefoot and Squee

Umbral Collar Zealot

How it works

1. Activate Umbral Collar Zealot twice by sacrificing Slimefoot and Squee and another nontoken creature.
2. When the creatures are sacrificed, Szarel triggers twice, putting a number of +1/+1 counters equal to twice Szarel's power on Crystalline Crawler.
3. Resolve the Umbral Collar Zealot abilities.
4. Activate Crystalline Crawler four times by removing four +1/+1 counters from it, adding 1.
5. Activate Slimefoot and Squee by paying 1 and sacrificing a Saproling, returning it and another creature from your graveyard to the battlefield.
6. When Slimefoot and Squee enters, it triggers, creating a 1/1 Saproling creature token.
7. Repeat.

This intricate loop transforms Crystalline Crawler into a self-sustaining mana battery, fueled by the recursive engine of Slimefoot and Squee. By utilizing Umbral Collar Zealot to sacrifice Slimefoot and Squee along with another creature, you trigger Szarel, Genesis Shepherd to pump up Crystalline Crawler with massive bursts of +1/+1 counters based on Szarel's power. Those counters are then stripped away for any color of mana to pay for Slimefoot and Squee's resurrection ability, which conveniently brings back your sacrificed fodder while dropping a fresh Saproling token to keep the sacrifice chain moving indefinitely.