Sporoloth Ancient, Tainted Observer, Ashnod's Altar, and Tekuthal, Inquiry Dominus

Prerequisites

• Sporoloth Ancient on the battlefield
• Tainted Observer on the battlefield
• Ashnod's Altar on the battlefield
• Tekuthal, Inquiry Dominus on the battlefield
• You control a creature with at least three spore counters on it

Steps

1. Activate a creature you control by removing two spore counters from it, creating a 1/1 Saproling creature token
2. The Saproling enters the battlefield, triggering Tainted Observer
3. Holding priority, activate Ashnod's Altar by sacrificing the Saproling, adding
4. Resolve the Tainted Observer trigger, causing you to pay to put two spore counters on any creature you control
5. Repeat

Results

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