Xavier Sal, Infested Captain, Intruder Alarm, and Sigil Captain

Prerequisites

• Xavier Sal, Infested Captain on the battlefield
• Intruder Alarm on the battlefield
• Sigil Captain on the battlefield
• undefined

Steps

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

Results

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