Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight, Altar of Dementia, and Cayth, Famed Mechanist

Prerequisites

• Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight on the battlefield
• Altar of Dementia on the battlefield
• Cayth, Famed Mechanist on the battlefield

Steps

1. Activate Altar of Dementia by sacrificing Cayth
2. When Cayth dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
3. When Cayth enters, its fabricate ability triggers, putting a +1/+1 counter on it
4. Resolve the Altar of Dementia ability
5. Repeat

Results

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