Panoptic Mirror, and Karn's Temporal Sundering

Prerequisites

• Panoptic Mirror on the battlefield
• Karn's Temporal Sundering in exile

Steps

1. At the beginning of your upkeep, Panoptic Mirror triggers, casting a copy of Karn's Temporal Sundering without paying its mana cost
2. Resolve Karn's Temporal Sundering, causing you to take an extra turn after this one
3. Repeat each turn

Results

• Infinite turns