Mikaeus, the Unhallowed + Altar of Dementia + Plague Belcher

Mikaeus, the Unhallowed

Altar of Dementia

Plague Belcher

How it works

1. Activate Altar of Dementia 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 Altar of Dementia ability
5. Repeat.