Deeproot Pilgrimage, Dack's Duplicate, and Forensic Researcher

Prerequisites

• Deeproot Pilgrimage on the battlefield
• Dack's Duplicate on the battlefield
• Forensic Researcher on the battlefield
• Dack's Duplicate on the battlefield as a copy of Forensic Researcher
• Forensic Researcher and Dack's Duplicate do not have summoning sickness

Steps

1. Activate Forensic Researcher by tapping it, targeting Dack's Duplicate
2. Deeproot Pilgrimage triggers, creating a 1/1 Merfolk creature token
3. Resolve the Forensic Researcher ability, untapping Dack's Duplicate
4. Activate Dack's Duplicate by tapping it, targeting Forensic Researcher
5. Deeproot Pilgrimage triggers, creating a 1/1 Merfolk creature token
6. Resolve the Dack's Duplicate ability, untapping Forensic Researcher
7. Repeat

Results

• Infinite ETB
• Infinite creature tokens