Mikaeus, the Unhallowed + Umbral Collar Zealot + Lingering Tormentor

Mikaeus, the Unhallowed

Umbral Collar Zealot

Lingering Tormentor

How it works

1. Activate Umbral Collar Zealot by sacrificing Lingering Tormentor.
2. When Lingering Tormentor dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Resolve the Umbral Collar Zealot ability.
4. Activate Umbral Collar Zealot by sacrificing Lingering Tormentor.
5. When Lingering Tormentor dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
6. Resolve the Umbral Collar Zealot ability.
7. Repeat.