Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight, Altar of Dementia, and Butcher Ghoul

Prerequisites

• Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight on the battlefield
• Altar of Dementia on the battlefield
• Butcher Ghoul on the battlefield

Steps

1. Activate Altar of Dementia by sacrificing Butcher Ghoul When Butcher Ghoul dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
2. Resolve the Altar of Dementia ability
3. Activate Altar of Dementia by sacrificing Butcher Ghoul When Butcher Ghoul dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
4. Butcher Ghoul enters and dies as a state-based action due to having 0 toughness
5. Its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
6. Resolve the Altar of Dementia ability from step 4
7. Repeat from step 4

Results

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