Calamity, Galloping Inferno, and Port Razer

Prerequisites

• Calamity, Galloping Inferno on the battlefield
• Port Razer on the battlefield
• An opponent cannot block creatures you control

Steps

1. Activate Calamity's saddle ability by tapping Port Razer, causing Calamity to become saddled until end of turn
2. Declare Calamity as an attacker
3. Calamity triggers, creating a tapped and attacking copy of Port Razer, and repeating the process once for any nonlegendary creature that saddled Calamity this turn
4. Deal combat damage using the Port Razer token(s)
5. Each Port Razer who has not attacked the opponent this turn triggers, causing you to untap each creature you control and to get that many additional combat phases after this one
6. Repeat from step 2 each combat phase

Results

• Infinite combat damage
• Infinite combat phases
• Infinite copies of any nonlegendary creature that saddled Calamity this turn
• Infinite creature tokens
• Infinite ETB
• Infinite mana creatures you control can produce
• Infinite untap of creatures you control