Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight, Altar of Dementia, and Geralf's Messenger

Prerequisites

• Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight on the battlefield
• Altar of Dementia on the battlefield
• Geralf's Messenger on the battlefield

Steps

1. Activate Altar of Dementia by sacrificing Geralf's Messenger When Geralf's Messenger dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
2. When Geralf's Messenger enters, it triggers, causing an opponent to lose 2 life
3. Activate Altar of Dementia by sacrificing Geralf's Messenger When Geralf's Messenger dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
4. When Geralf's Messenger enters, it triggers, causing an opponent to lose 2 life
5. Resolve both Altar of Dementia abilities from step 1 and 4
6. Repeat

Results

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