Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight, Sin, Unending Cataclysm, and Carrion Feeder

Prerequisites

• Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight on the battlefield
• Sin, Unending Cataclysm on the battlefield
• Carrion Feeder on the battlefield

Steps

1. Activate Carrion Feeder by sacrificing the additional creature
2. When the creature dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
3. Resolve the Carrion Feeder ability
4. Activate Carrion Feeder by sacrificing Sin
5. When Sin dies, it triggers twice
6. Resolve the first trigger, returning Sin from your graveyard to the battlefield with a -1/-1 counter on it
7. As Sin enters, remove the -1/-1 counter from the creature sacrificed in step 1, causing Sin to enter with a +1/+1 counter on it instead
8. Resolve the second Sin trigger, putting the counters it had on it when it was sacrificed onto a creature you control and failing to shuffle it into your library as it's no longer in your graveyard
9. Resolve the Carrion Feeder ability from step 4
10. Repeat

Results

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