Mikaeus, the Unhallowed + Umbral Collar Zealot + Plague Belcher

Mikaeus, the Unhallowed

Umbral Collar Zealot

Plague Belcher

How it works

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