Éomer, Marshal of Rohan, Kari Zev, Skyship Raider, Helm of the Host, and Ashnod's Altar

Prerequisites

• Éomer, Marshal of Rohan on the battlefield
• Kari Zev, Skyship Raider on the battlefield
• Helm of the Host on the battlefield
• Ashnod's Altar on the battlefield
• Helm of the Host attached to Éomer
• Kari Zev does not have summoning sickness and cannot be blocked and killed by an opponent

Steps

1. At the beginning of your combat phase, Helm of the Host triggers, creating a nonlegendary token copy of Éomer with haste
2. Declare Kari Zev as an attacker
3. Kari Zev triggers, creating a legendary 2/1 Ragavan creature token that is tapped and attacking
4. Holding priority, activate Ashnod's Altar by sacrificing Ragavan, adding
5. When Ragavan dies, each Éomer that hasn't triggered this turn triggers, untapping all creatures you control and causing you to get at least one additional combat phase after this one
6. Repeat each combat phase

Results

• Infinite combat phases
• Infinite creature tokens with haste
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers