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

Prerequisites

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

Steps

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

Results

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