Lesser Masticore + Mm'menon, Uthros Exile + Phantom Train

Lesser Masticore

Mm'menon, Uthros Exile

Phantom Train

How it works

1. Activate Phantom Train 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 Phantom Train ability.
5. Repeat.

This clever loop centers on Lesser Masticore and its persist ability, which normally self-terminates after a single recursion due to the -1/-1 counter it returns with. By utilizing Phantom Train to sacrifice the Masticore, you send it back to the graveyard to feed that persist trigger, while simultaneously turning the Train into an active creature. The real magic happens when Lesser Masticore returns to the battlefield, triggering Mm'menon, Uthros Exile to place a +1/+1 counter on it; state-based actions then cause the +1/+1 and -1/-1 counters to annihilate one another, resetting the Masticore so it can be sacrificed to the Train all over again.