Fain, the Broker + Chatterfang, Squirrel General + Intruder Alarm + Metallic Mimic
Fain, the Broker
Chatterfang, Squirrel General
Intruder Alarm
Metallic Mimic
Infinite artifact ETBInfinite artifact LTBInfinite artifact sacrifice triggersInfinite artifact tokensInfinite colored manaInfinite creature tokensInfinite death triggersInfinite creature ETBInfinite creature LTBInfinite mana creatures you control can produceInfinite creature sacrifice triggersInfinite Treasure tokensInfinite untap of creaturesReduce the toughness of creatures opponents control to 0Infinite +1/+1 counters on creatures you control
How it works
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.
When the Squirrel enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Repeat.
Once you have infinite Treasure and Squirrel tokens, you may activate Fain's other abilities.
This loop is a masterclass in token generation, where Fain, the Broker acts as the engine by trading a counter from a creature to create a Treasure token. Chatterfang, Squirrel General watches this happen and doubles the yield by tagging on an extra Squirrel token whenever any other token is created. This is where Metallic Mimic shines as a passive enabler: by naming Squirrel as its type, it ensures every generated Squirrel enters the battlefield with an extra +1/+1 counter already on it. That fresh counter supplies Fain, the Broker with the exact resource it needs to keep going, while the creature entry triggers Intruder Alarm to untap your board and let you repeat the process indefinitely for infinite resources.