Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight, Cayth, Famed Mechanist, and Yahenni, Undying Partisan

Prerequisites

• Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight on the battlefield
• Cayth, Famed Mechanist on the battlefield
• Yahenni, Undying Partisan on the battlefield

Steps

1. Activate Yahenni 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 Yahenni ability
5. Repeat

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers