Sporoloth Ancient, Tainted Observer, Ashnod's Altar, and Doubling Season

Prerequisites

• Sporoloth Ancient on the battlefield
• Tainted Observer on the battlefield
• Ashnod's Altar on the battlefield
• Doubling Season 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 two 1/1 Saproling creature tokens
2. The Saprolings enter the battlefield, triggering Tainted Observer twice
3. Holding priority, activate Ashnod's Altar by sacrificing a Saproling, adding
4. Resolve the first Tainted Observer trigger, causing you to pay to put two spore counters on any creature you control
5. Resolve the second Tainted Observer trigger, choosing not to pay
6. Repeat

Results

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