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
Grumgully.
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.
Results
Infinite artifact ETB.
Infinite artifact LTB.
Infinite artifact sacrifice triggers.
Infinite artifact tokens.
Infinite colored mana.
Infinite creature tokens.
Infinite death triggers.
Infinite creature ETB.
Infinite creature LTB.
Infinite mana creatures you control can produce.
Infinite creature sacrifice triggers.
Infinite Treasure tokens.
Infinite untap of creatures.
Reduce the toughness of creatures opponents control to 0.
Infinite +1/+1 counters on creatures you control.
Metadata
In 0 decks according to EDHREC.
Bracket Tag
This combo has been estimated to be Exhibition (Bracket 1+).