Progenitor Mimic, Capture of Jingzhou, and Eternal Witness

Prerequisites

• Progenitor Mimic on the battlefield
• Capture of Jingzhou on the battlefield
• Eternal Witness on the battlefield
• Enough mana available to cast the extra turn spell each turn
• Progenitor Mimic is a copy of Eternal Witness

Steps

1. Cast Capture of Jingzhou by paying its mana cost, taking an extra turn after this one
2. At the beginning of your next upkeep, Progenitor Mimic triggers, creating a token copy of Eternal Witness
3. When the token Eternal Witness enters the battlefield, it triggers itself, returning Capture of Jingzhou from your graveyard to your hand
4. Repeat

Results

• Infinite turns