Koh, the Face Stealer, and Port Razer

Prerequisites

• Koh, the Face Stealer on the battlefield
• Port Razer in exile

Steps

1. Activate Koh by paying 1 life, causing it to gain Port Razer's triggered and activated abilities
2. Deal combat damage using Koh, triggering Koh, causing you to untap all creatures you control and to get an additional combat phase after this one
3. Repeat step 2 each combat phase

Results

• Infinite combat phases
• Infinite untap of creatures you control
• Infinite mana creatures you control can produce
• Infinite combat damage