Mikaeus, the Unhallowed, and Altar of Dementia

Prerequisites

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

Steps

1. Activate Altar of Dementia by sacrificing the persist creature
2. When the persist creature dies, its persist ability triggers if it didn't have a -1/-1 counter on it, and its undying ability triggers if it didn't have a +1/+1 counter on it
3. Resolve the persist trigger, if applicable, returning the creature from your graveyard to the battlefield with a -1/-1 counter on it
4. Resolve the undying trigger, if applicable, returning the creature from your graveyard to the battlefield with a +1/+1 counter on it
5. Resolve the Altar of Dementia ability
6. Repeat

Results

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