Mardu Siegebreaker, and Bloodthirster

Prerequisites

• Mardu Siegebreaker on the battlefield
• Bloodthirster in exile

Steps

1. Declare Mardu Siegebreaker as an attacker, triggering its second ability, creating a token copy of Bloodthirster that is tapped and attacking
2. Deal combat damage with the Bloodthirster token, triggering its ability, untapping Mardu Siegebreaker and causing you to get an additional combat phase after this one
3. Repeat each combat phase

Results

• Infinite ETB
• Infinite combat phases
• Infinite LTB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinite combat damage
• Infinite tapped creature tokens