Veinwitch Coven, Zulaport Cutthroat, and Phyrexian Altar

Prerequisites

• Veinwitch Coven on the battlefield
• Zulaport Cutthroat on the battlefield
• Phyrexian Altar on the battlefield

Steps

1. Activate Phyrexian Altar by sacrificing the one-drop creature, adding
2. When that creature dies, it and Zulaport Cutthroat trigger
3. Resolve the creature's ability, creating a creature token
4. Resolve the Zulaport Cutthroat ability, gaining at least one life and causing at least one opponent to lose at least one life
5. When you gain life, Veinwitch Coven triggers, causing you to pay to return the one-drop creature from your graveyard to your hand
6. Activate Phyrexian Altar by sacrificing the token creature, adding one colored mana
7. Cast the creature by paying one mana
8. Repeat

Results

• Infinite creature ETB
• Infinite creature LTB
• Infinite creature sacrifice triggers
• Infinite death triggers
• Infinite lifegain