Veinwitch Coven, Vindictive Vampire, and Phyrexian Altar

Prerequisites

• Veinwitch Coven on the battlefield
• Vindictive Vampire 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 Vindictive Vampire trigger
3. Resolve the creature's ability, creating a creature token
4. Resolve the Vindictive Vampire ability, gaining 1 life and causing Vindictive Vampire to deal 1 damage to each opponent
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
• Infinite damage