Mardu Siegebreaker, and Wispweaver Angel

Prerequisites

• Mardu Siegebreaker on the battlefield
• Wispweaver Angel in exile

Steps

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

Results

• Infinite LTB
• Infinite ETB