Stangg, Echo Warrior, Éomer, Marshal of Rohan, and Helm of the Host

Prerequisites

• Stangg, Echo Warrior on the battlefield
• Éomer, Marshal of Rohan on the battlefield
• Helm of the Host on the battlefield
• Helm of the Host attached to Éomer
• Stangg does not have summoning sickness
• An opponent cannot block and kill Stangg
• You control another legendary creature that can attack this turn
• You have a way to kill the additional legendary creature at instant speed

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 Stangg and the additional legendary creature as attackers
3. Stangg triggers, creating a 3/4 Stangg Twin creature token that is tapped and attacking
4. Holding priority, kill the additional legendary creature
5. When the creature dies, each Éomer that has not triggered this turn triggers, causing you to untap all creatures you control and to get at least one additional combat phase after this one
6. Move to your next combat phase
7. At the beginning of your combat phase, Helm of the Host triggers, creating a nonlegendary token copy of Éomer with haste
8. Declare Stangg as an attacker
9. Stangg triggers, creating a 3/4 Stangg Twin creature token that is tapped and attacking
10. Put either Stangg Twin token into your graveyard due to the legend rule
11. Repeat from step 5

Results

• Infinite combat phases
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite mana creatures you control can produce
• Infinite untap of creatures you control