Krark-Clan Grunt + Lesser Masticore + Mm'menon, Uthros Exile

Krark-Clan Grunt

Lesser Masticore

Mm'menon, Uthros Exile

How it works

1. Activate Krark-Clan Grunt 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. When Lesser Masticore enters, Mm'menon triggers, putting a +1/+1 counter on Lesser Masticore.
4. Resolve the Krark-Clan Grunt ability.
5. Repeat.

This loop relies on the clever interplay between Lesser Masticore's persist ability and the artifact sacrifice outlet provided by Krark-Clan Grunt, which continuously bins the rat to fuel its own power boost. Because persist normally locks a creature out of returning if it already has a -1/-1 counter, Mm'menon, Uthros Exile steps in as the crucial enabler: every time Lesser Masticore enters the battlefield as an artifact, Mm'menon's triggered ability places a +1/+1 counter on it. State-based actions then cause the +1/+1 and -1/+1 (or -1/-1) counters to annihilate each other, resetting Lesser Masticore with a clean slate and letting you repeat the execution indefinitely.