Xavier Sal, Infested Captain, Intruder Alarm, and Good-Fortune Unicorn

Prerequisites

• Xavier Sal, Infested Captain on the battlefield
• Intruder Alarm on the battlefield
• Good-Fortune Unicorn 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 Good-Fortune Unicorn trigger
3. Resolve the Intruder Alarm trigger, untapping all creatures
4. Resolve the Good-Fortune Unicorn trigger, putting a +1/+1 counter on the creature token
5. Repeat

Results

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