Mardu Siegebreaker, and Restoration Angel

Prerequisites

• Mardu Siegebreaker on the battlefield
• Restoration Angel in exile

Steps

1. Declare Mardu Siegebreaker as an attacker, triggering its second ability, creating at least one token copy of Restoration Angel that is tapped and attacking
2. When the Restoration Angel token(s) enter the battlefield, they trigger
3. Resolve the first trigger, blinking Mardu Siegebreaker
4. Mardu Siegebreaker leaves and enters the battlefield, causing the nontoken Restoration Angel to return to the battlefield from exile, and triggering Restoration Angel and Mardu Siegebreaker's first ability
5. Resolve the Mardu Siegebreaker trigger, exiling the nontoken Restoration Angel until Mardu Siegebreaker leaves the battlefield
6. Resolve the Restoration Angel trigger, blinking Mardu Siegebreaker
7. Repeat from step 4

Results

• Infinite LTB
• Infinite ETB