Mikaeus, the Unhallowed + Yahenni, Undying Partisan

Mikaeus, the Unhallowed

Yahenni, Undying Partisan

How it works

1. Activate Yahenni by sacrificing the creature with persist.
2. When that creature 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 the persist creature.
5. When the persist creature 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.