Mikaeus, the Unhallowed + Lesser Masticore + Yahenni, Undying Partisan

Mikaeus, the Unhallowed

Lesser Masticore

Yahenni, Undying Partisan

How it works

1. Activate Yahenni 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. Resolve the Yahenni ability.
4. Activate Yahenni by sacrificing Lesser Masticore.
5. When Lesser Masticore dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
6. Resolve the Yahenni ability.
7. Repeat.