Tenacious Dead, Ashnod's Altar, and Pitiless Plunderer

Prerequisites

• Tenacious Dead on the battlefield
• Ashnod's Altar on the battlefield
• Pitiless Plunderer on the battlefield

Steps

1. Activate Ashnod's Altar by sacrificing Tenacious Dead, adding
2. When Tenacious Dead dies, it and Pitiless Plunderer trigger
3. Resolve the Pitiless Plunderer trigger, creating a Treasure token
4. Activate that Treasure token by tapping and sacrificing it, adding
5. Resolve the Tenacious Dead trigger, paying to return it to the battlefield from your graveyard
6. Repeat

Results

• Infinite colorless mana
• Infinite creature ETB
• Infinite creature LTB
• Infinite creature sacrifice triggers
• Infinite death triggers