Intruder Alarm, and Deeproot Pilgrimage

Prerequisites

• Intruder Alarm on the battlefield
• Deeproot Pilgrimage on the battlefield
• The Merfolk does not have summoning sickness
• There are legal targets for the Merfolk's ability, if applicable

Steps

1. Activate the Merfolk by tapping it
2. Deeproot Pilgrimage triggers, creating a 1/1 Merfolk creature token
3. When the Merfolk enters the battlefield, Intruder Alarm triggers, untapping all creatures
4. Resolve the Merfolk's tap ability
5. Repeat

Results

• Infinite ETB
• Infinite creature tokens
• Infinite untap of all creatures
• Infinite mana creatures you control can produce
• Infinite instances of the tapped creature's ability