Szarel, Genesis Shepherd + Crystalline Crawler + Umbral Collar Zealot + Cult Conscript

Szarel, Genesis Shepherd

Crystalline Crawler

Umbral Collar Zealot

Cult Conscript

How it works

1. Activate Cult Conscript by paying 1, returning it from your graveyard to the battlefield.
2. Activate Umbral Collar Zealot by sacrificing Cult Conscript.
3. When Cult Conscript is sacrificed, Szarel triggers, putting a number of +1/+1 counters equal to Szarel's power on Crystalline Crawler.
4. Resolve the Umbral Collar Zealot ability.
5. Activate Crystalline Crawler twice by removing two +1/+1 counters from it, adding 1.
6. Repeat.

This clever loop hinges on a continuous cycle of sacrifice and recursion, fueled entirely by Crystalline Crawler's unique ability to convert its own +1/+1 counters into the exact mana needed to keep the engine running. By paying to return Cult Conscript from the graveyard to the battlefield, you feed fodder to Umbral Collar Zealot, whose sacrifice ability triggers Szarel, Genesis Shepherd to pump up Crystalline Crawler with a massive influx of counters thanks to Szarel's power. Each time Cult Conscript dies, it satisfies its own recursion condition while letting Umbral Collar Zealot's surveil trigger filter through your deck, ultimately generating infinite mana, triggers, and growth for your board.