Mikaeus, the Unhallowed + Viscera Seer + Plague Belcher

Mikaeus, the Unhallowed

Viscera Seer

Plague Belcher

How it works

1. Activate Viscera Seer 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 Viscera Seer ability
5. Repeat.