Mikaeus, the Unhallowed, Plague Belcher, and Altar of Dementia

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Plague Belcher on the battlefield
• Altar of Dementia on the battlefield

Steps

1. Activate Altar of Dementia by sacrificing Plague Belcher
2. Plague Belcher dies, triggering its undying ability, returning it from your graveyard to the battlefield with a +1/+1 counter on it
3. Plague Belcher enters the battlefield, putting two -1/-1 counters on itself
4. Resolve the Altar of Dementia ability, causing target player to mill cards equal to Plague Belcher's power
5. Repeat

Results

• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite mill
• Infinite sacrifice triggers
• Infinite self-mill