Tainted Observer, Mana Echoes, and Saproling Burst

Prerequisites

• Tainted Observer on the battlefield
• Mana Echoes on the battlefield
• Saproling Burst on the battlefield
• Saproling Burst has at least two fade counters on it
• if you don't control at least one Saproling available

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 and Mana Echoes triggers
3. Resolve the Mana Echoes trigger, adding for each Saproling you control
4. Resolve the Tainted Observer trigger, causing you to pay to put a fade counter on Saproling Burst
5. Repeat

Results

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