Xavier Sal, Infested Captain, Intruder Alarm, and Dragonspark Reactor

Prerequisites

• Xavier Sal, Infested Captain on the battlefield
• Intruder Alarm on the battlefield
• Dragonspark Reactor on the battlefield
• You control at least one artifact creature token
• Xavier Sal does not have summoning sickness
• There is a removable counter on a permanent you control

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 Dragonspark Reactor trigger
3. Resolve the Intruder Alarm trigger, untapping all creatures
4. Resolve the Dragonspark Reactor trigger, putting a counter on it
5. Repeat

Results

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