Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight, Carrion Feeder, and Witch-king, Sky Scourge

Prerequisites

• Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight on the battlefield
• Carrion Feeder on the battlefield
• Witch-king, Sky Scourge on the battlefield

Steps

1. Activate Carrion Feeder by sacrificing Witch-king When Witch-king dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
2. Activate Carrion Feeder by sacrificing Witch-king When Witch-king dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
3. Resolve both Carrion Feeder abilities from step 1 and 3
4. Repeat

Results

• Infinite +1/+1 counters on a creature
• Infinite ETB
• Infinite LTB
• Infinite death triggers
• Infinite sacrifice triggers