Fain, the Broker, Chatterfang, Squirrel General, Intruder Alarm, and Metallic Mimic

Prerequisites

• Fain, the Broker on the battlefield
• Chatterfang, Squirrel General on the battlefield
• Intruder Alarm on the battlefield
• Metallic Mimic on the battlefield
• Fain does not have summoning sickness
• "Squirrel" chosen with Metallic Mimic

Steps

1. Activate Fain's second ability by tapping it and removing a counter from a creature you control, creating a Treasure artifact token and a 1/1 Squirrel creature token that enters the battlefield with a +1/+1 counter on it due to Metallic Mimic
2. When the Squirrel enters the battlefield, Intruder Alarm triggers, untapping all creatures
3. Repeat
4. Once you have infinite Treasure and Squirrel tokens, you may activate Fain's other abilities

Results

• Infinite +1/+1 counters
• Infinite colored mana
• Infinite creature tokens
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite mana creatures you control can produce
• Infinite sacrifice triggers
• Infinite Treasure tokens
• Infinite untap of all creatures