Tainted Observer, Ashnod's Altar, and Saproling Burst

Prerequisites

• Tainted Observer on the battlefield
• Ashnod's Altar on the battlefield
• Saproling Burst on the battlefield

Steps

1. Activate Saproling Burst by removing a fade counter from it, creating a */* Saproling creature token
2. When the Saproling enters the battlefield, Tainted Observer triggers
3. Holding priority, activate Ashnod's Altar by sacrificing the Saproling, adding
4. Resolve the Tainted Observer trigger, causing you to pay to put a fade counter on Saproling Burst
5. Repeat

Results

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