Xavier Sal, Infested Captain, Intruder Alarm, and Bloodline Pretender

Prerequisites

• Xavier Sal, Infested Captain on the battlefield
• Intruder Alarm on the battlefield
• Bloodline Pretender on the battlefield
• You control at least one creature token
• Xavier Sal does not have summoning sickness
• There is a removable counter on a permanent you control
• Bloodline Pretender naming the same type as a creature token you control

Steps

1. Activate Xavier Sal by tapping it and removing a counter from a permanent you control, creating a copy of a creature token you control
2. When the creature token enters the battlefield, Intruder Alarm and Bloodline Pretender trigger
3. Resolve the Intruder Alarm trigger, untapping all creatures
4. Resolve the Bloodline Pretender 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