Bloodspore Thrinax has at least two +1/+1 counters on it.
Steps
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 with at least one +1/+1 counter on it due to
Bloodspore Thrinax.
The Squirrel enters the battlefield, triggering
Intruder Alarm, untapping all creatures.
Repeat.
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 ETB.
Infinite mana creatures you control can produce.
Infinite Treasure tokens.
Infinite LTB.
Infinite sacrifice triggers.
Infinite death triggers.
Reduce any number of target creatures' toughness to 0.