Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight, Ceti Eel, and Yahenni, Undying Partisan

Prerequisites

• Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight on the battlefield
• Ceti Eel on the battlefield
• Yahenni, Undying Partisan on the battlefield

Steps

1. Activate Yahenni by sacrificing Ceti Eel
2. When Ceti Eel dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
3. When Ceti Eel enters, it triggers, causing you to mill two cards and put a +1/+1 counter on it
4. Resolve the Yahenni ability
5. Repeat

Results

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