Combat Celebrant, and Splinter Twin

Prerequisites

• Combat Celebrant on the battlefield
• Splinter Twin on the battlefield

Steps

1. Activate Combat Celebrant by tapping it, making a token copy of itself with haste
2. Proceed to your combat step
3. Declare the Combat Celebrant copy as an attacker, choosing to exert it as it attacks
4. The Combat Celebrant copy triggers, untapping all other creatures you control and causing you to get an additional combat phase after this one
5. Repeat

Results

• Infinite combat phases
• Infinite creature tokens with haste
• Infinite ETB