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

Prerequisites

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

Steps

1. Activate Thermopod by sacrificing it When Thermopod dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
2. Activate Thermopod by sacrificing Sin
3. When Sin dies, it triggers twice
4. Resolve the first trigger, returning Sin from your graveyard to the battlefield with a -1/-1 counter on it
5. As Sin enters, remove the -1/-1 counter from Thermopod, causing Sin to enter with a +1/+1 counter on it instead
6. 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
7. Repeat

Results

• Infinite ETB
• Infinite LTB
• Infinite death triggers
• Infinite red mana
• Infinite sacrifice triggers