Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight, Phyrexian Altar, and Witch-king, Sky Scourge

Prerequisites

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

Steps

1. Activate Phyrexian Altar 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 Phyrexian Altar 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. Repeat

Results

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