Altaïr Ibn-La'Ahad, Bloodthirster, and Rukarumel, Biologist

Prerequisites

• Altaïr Ibn-La'Ahad on the battlefield
• Bloodthirster in the graveyard
• Rukarumel, Biologist on the battlefield
• "Assassin" chosen with Rukarumel
• An opponent cannot block creatures you control
• You have a way to give Altaïr Ibn-La'Ahad vigilance

Steps

1. Give Altaïr Ibn-La'Ahad vigilance by any method
2. Declare Altaïr Ibn-La'Ahad as an attacker
3. Altaïr Ibn-La'Ahad triggers, exiling Bloodthirster from your graveyard with a memory counter on it as it is an Assassin due to Rukarumel, and then creating a tapped and attacking token copy of each creature you own in exile with a memory counter on it
4. Deal combat damage to an opponent using the Bloodthirster token
5. The Bloodthirster token triggers, causing you to untap it and to get an additional combat phase after this one
6. At the end of your combat phase, Altaïr Ibn-La'Ahad triggers, exiling the Bloodthirster token
7. Move to your next combat phase, and declare Altaïr Ibn-La'Ahad as an attacker
8. Altaïr Ibn-La'Ahad triggers, creating a tapped and attacking token copy of each creature you own in exile with a memory counter on it
9. Repeat from step 4

Results

• Infinite combat damage
• Infinite combat phases
• Infinite ETB
• Infinite LTB