Altaïr Ibn-La'Ahad, Éomer, Marshal of Rohan, Yahenni, Undying Partisan, and Maskwood Nexus

Prerequisites

• Altaïr Ibn-La'Ahad on the battlefield
• Éomer, Marshal of Rohan in the graveyard
• Yahenni, Undying Partisan on the battlefield
• Maskwood Nexus on the battlefield
• Altaïr does not have summoning sickness
• An opponent cannot block and kill Altaïr
• You have at least one legendary creature card exiled with a memory counter on it

Steps

1. Declare Altaïr as an attacker
2. Altaïr triggers, exiling Éomer from your graveyard with a memory counter on it, and then creating a tapped and attacking token copy of each card you own that is exiled with a memory counter on it
3. Activate Yahenni by sacrificing another legendary creature token except Éomer
4. When the creature dies, Éomer triggers, untapping all creatures you control and causing you to get an additional combat phase after this one
5. Resolve the Yahenni ability
6. Repeat during each combat phase

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinite combat phases