Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight, Mikaeus, the Unhallowed, and Altar of Dementia

Prerequisites

• Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight on the battlefield
• Mikaeus, the Unhallowed on the battlefield
• Altar of Dementia on the battlefield

Steps

1. Activate Altar of Dementia by sacrificing another nontoken non-Human creature When the creature dies, its undying ability triggers, returning the creature from your graveyard to the battlefield with a +1/+1 counter on it
2. Activate Altar of Dementia by sacrificing the creature with a +1/+1 counter on it
3. When the creature dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
4. Resolve the Altar of Dementia abilities from step 1 and 3
5. Repeat

Results

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