Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight, Yahenni, Undying Partisan, and Butcher Ghoul

Prerequisites

• Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight on the battlefield
• Yahenni, Undying Partisan on the battlefield
• Butcher Ghoul on the battlefield

Steps

1. Activate Yahenni by sacrificing Butcher Ghoul When Butcher Ghoul dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
2. Resolve the Yahenni ability
3. Activate Yahenni by sacrificing Butcher Ghoul When Butcher Ghoul dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
4. Butcher Ghoul enters and dies as a state-based action due to having 0 toughness
5. Its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
6. Resolve the Yahenni ability from step 4
7. Repeat from step 4

Results

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