Xavier Sal, Infested Captain, Intruder Alarm, and Cathars' Crusade

Prerequisites

• Xavier Sal, Infested Captain on the battlefield
• Intruder Alarm on the battlefield
• Cathars' Crusade on the battlefield
• There is at least one counter on a permanent you control
• You control at least one creature token

Steps

1. Activate Xavier Sal's first ability by tapping it and removing a counter from a permanent you control, creating a copy of any creature token you control
2. When the creature token enters the battlefield, Intruder Alarm and Cathars' Crusade trigger
3. Resolve the Intruder Alarm trigger, untapping all creatures
4. Resolve the Cathars' Crusade trigger, putting a +1/+1 counter on each creature you control
5. Repeat

Results

• Infinite creature tokens
• Infinite ETB
• Infinite mana creatures you control can produce
• Infinite untap of all creatures
• Infinite +1/+1 counters