Charnelhoard Wurm as an attacker, triggering its firebending ability, adding ({R} magic symbol) ({R} magic symbol) ({R} magic symbol) ({R} magic symbol) ({R} magic symbol) .
Holding priority, cast
Great Train Heist by paying ({2} magic symbol) ({R} magic symbol) ({R} magic symbol) , selecting its first mode, causing you to untap all creatures you control and get an additional combat phase after this one.
Deal combat damage using
Charnelhoard Wurm, triggering its ability, returning
Great Train Heist from your graveyard to your hand.
Repeat from step 2.
Notes
You can attack with additional creatures for additional ({R} magic symbol) and choose more modes using
Great Train Heist.
Results
Infinite storm count.
Infinite combat phases.
Infinite untap of creatures you control.
Infinite mana creatures you control can produce.
Infinite tapped Treasure tokens.
Infinite magecraft triggers.
Infinite combat damage.
Infinitely powerful creatures you control until end of turn.