Isochron Scepter, To Arms!, and Karn, Silver Golem

Prerequisites

• Isochron Scepter on the battlefield
• To Arms! in exile
• Karn, Silver Golem on the battlefield
• available

Steps

1. Activate Karn by paying , causing Isochron Scepter to become an artifact creature until end of turn
2. Activate creatures you control by tapping those, adding
3. Activate Isochron Scepter by paying and tapping it, casting a copy of To Arms! without paying its mana cost, untapping all creatures
4. Repeat from step 2

Results

• Infinite mana creatures you control can produce
• Infinite storm count