Phantom Steed, and Port Razer

Prerequisites

• Phantom Steed on the battlefield
• Port Razer in exile
• Phantom Steed does not have summoning sickness
• An opponent is unable to block and kill creatures you control

Steps

1. Declare Phantom Steed as an attacker, attacking any opponent that is unable to block and kill your creatures
2. Phantom Steed's second ability triggers, creating a tapped and attacking copy of Port Razer
3. Deal combat damage with Phantom Steed and Port Razer
4. Port Razer triggers, causing you to untap all creatures you control and get an additional combat phase after this one
5. At the end of your combat phase, Phantom Steed triggers, causing you to sacrifice the Port Razer token
6. Repeat each combat phase

Results

• Infinite combat damage
• Infinite combat phases
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers
• Infinite untap of creatures you control