Deeproot Pilgrimage, Mercurial Pretender, and Forensic Researcher

Prerequisites

• Deeproot Pilgrimage on the battlefield
• Mercurial Pretender on the battlefield
• Forensic Researcher on the battlefield
• Mercurial Pretender on the battlefield as a copy of Forensic Researcher
• Forensic Researcher and Mercurial Pretender do not have summoning sickness

Steps

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

Results

• Infinite ETB
• Infinite creature tokens