Umbral Collar Zealot + Lesser Masticore + Thran Vigil

Umbral Collar Zealot

Lesser Masticore

Thran Vigil

How it works

1. Activate Umbral Collar Zealot by sacrificing Lesser Masticore.
2. When Lesser Masticore dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Thran Vigil triggers, putting a +1/+1 counter on Lesser Masticore.
4. Resolve the Umbral Collar Zealot ability.
5. Repeat.

This cunning loop centers around Lesser Masticore and its persist ability, which normally would exhaust itself after a single death once a -1/-1 counter is applied. However, Thran Vigil acts as the crucial engine piece, observing whenever Lesser Masticore leaves the graveyard to trigger and place a +1/+1 counter on it; when these opposing counters meet, they instantly annihilate each other as a state-based action, leaving the creature completely clean and ready to persist again. Meanwhile, Umbral Collar Zealot provides the necessary sacrifice outlet to keep the cycle turning while continuously surveilling your library.