Xavier Sal, Infested Captain, Intruder Alarm, and Kappa Cannoneer

Prerequisites

• Xavier Sal, Infested Captain on the battlefield
• Intruder Alarm on the battlefield
• Kappa Cannoneer on the battlefield

Steps

1. Activate Xavier Sal by tapping it and removing a counter from a permanent you control, creating a copy of an artifact creature token you control
2. When the creature token enters the battlefield, Intruder Alarm and Kappa Cannoneer trigger
3. Resolve the Intruder Alarm trigger, untapping all creatures
4. Resolve the Kappa Cannoneer trigger, putting a counter on it
5. Repeat

Results

• Infinite ETB
• Infinite creature tokens
• Infinite mana creatures you control can produce
• Infinite untap of all creatures
• Infinite copies of creature tokens you control