Mikaeus, the Unhallowed, Grim Poppet, and Altar of Dementia

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Grim Poppet on the battlefield
• Altar of Dementia on the battlefield

Steps

1. Activate Altar of Dementia by sacrificing Grim Poppet
2. Grim Poppet dies, triggering its undying ability, returning it from your graveyard to the battlefield with two -1/-1 counters on it
3. Resolve the Altar of Dementia ability, causing target player to mill cards equal to Grim Poppet's power
4. Repeat

Results

• Infinite -1/-1 counters
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite mill
• Infinite sacrifice triggers
• Infinite self-mill