Progenitor Mimic, Time Stretch, and Timeless Witness

Prerequisites

• Progenitor Mimic on the battlefield
• Time Stretch in hand
• Timeless Witness on the battlefield
• each other turn available

Steps

1. Cast Time Stretch 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 Timeless Witness
3. When the token Timeless Witness enters the battlefield, it triggers itself, returning Time Stretch from your graveyard to your hand
4. Repeat during your second extra turn

Results

• Infinite turns