Urza, Chief Artificer, Time Sieve, Myr Battlesphere, and Teleportation Circle

Prerequisites

• Urza, Chief Artificer on the battlefield
• Time Sieve on the battlefield
• Myr Battlesphere on the battlefield
• Teleportation Circle on the battlefield

Steps

1. At the beginning of your end step, Teleportation Circle and Urza trigger
2. Resolve the Urza trigger, creating a 0/0 Construct creature token
3. Resolve the Teleportation Circle trigger, blinking Myr Battlesphere
4. When Myr Battlesphere enters the battlefield, its first ability triggers, creating four 1/1 Myr artifact creature tokens
5. Activate Time Sieve by tapping it and sacrificing the Myrs and Construct, causing you to take an extra turn after this one
6. Repeat each turn

Results

• Infinite turns