Wormfang Manta, Phelia, Exuberant Shepherd, and Karn, Argent Defender

Prerequisites

• Wormfang Manta on the battlefield
• Phelia, Exuberant Shepherd on the battlefield
• Karn, Argent Defender on the battlefield

Steps

1. Declare Phelia as an attacker, attacking a player that cannot kill it in combat
2. When Phelia attacks, it triggers, exiling and returning (at end step) Wormfang Manta
3. When Wormfang Manta leaves the battlefield, its second ability triggers, causing you to take an extra turn after this one
4. Wormfang Manta entering does not cause its abillity to trigger due to Karn
5. Repeat each turn

Results

• Infinite turns
• Lock